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`
`Email - Wikipedia
`
`Email
`
`Electronic mail (email or e-mail) is a method of exchanging messages
`("mail") between people using electronic devices. Email first entered limited
`use in the 1960s and by the mid-1970s had taken the form now recognized as
`email. Email operates across computer networks, which today is primarily the
`Internet. Some early email systems required the author and the recipient to
`both be online at the same time, in common with instant messaging. Today's
`email systems are based on a store-and-forward model. Email servers accept,
`forward, deliver, and store messages. Neither the users nor their computers are
`required to be online simultaneously; they need to connect only briefly,
`typically to a mail server or a webmail interface, for as long as it takes to send
`or receive messages.
`
`Originally an ASCII text-only communications medium, Internet email was
`extended by Multipurpose Internet Mail Extensions (MIME) to carry text in
`other character sets and multimedia content attachments. International email,
`with internationalized email addresses using UTF-8, has been standardized,
`but as of 2017 it has not been widely adopted.[2]
`
`The history of modern Internet email services reaches back to the early
`ARPANET, with standards for encoding email messages published as early as
`1973 (RFC 561). An email message sent in the early 1970s looks very similar to
`a basic email sent today. Email had an important role in creating the
`Internet,[3] and the conversion from ARPANET to the Internet in the early
`1980s produced the core of the current services.
`
`Contents
`Terminology
`Origin
`Operation
`Message format
`Message header
`Header fields
`Message body
`Content encoding
`Plain text and HTML
`Servers and client applications
`Filename extensions
`URI scheme mailto
`Types
`Web-based email
`
`This screenshot shows the "Inbox"
`page of an email client, where users
`can see new emails and take
`actions, such as reading, deleting,
`saving, or responding to these
`messages
`
`The at sign, a part of every SMTP
`email address[1]
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`Email - Wikipedia
`
`POP3 email services
`IMAP email servers
`MAPI email servers
`Uses
`Business and organizational use
`Email marketing
`Personal use
`Personal computer
`Mobile
`Declining use among young people
`
`Issues
`Attachment size limitation
`Information overload
`Spam
`Malware
`Email spoofing
`Email bombing
`Privacy concerns
`Flaming
`Email bankruptcy
`Internationalization
`Tracking of sent mail
`See also
`References
`Further reading
`External links
`
`Terminology
`
`Historically, the term electronic mail was used generically for any electronic document transmission. For example, several
`writers in the early 1970s used the term to describe fax document transmission.[4][5] As a result, it is difficult to find the
`first citation for the use of the term with the more specific meaning it has today.
`
`Electronic mail has been most commonly called email or e-mail since around 1993,[6] but variations of the spelling have
`been used:
`
`email is the most common form used online, and is required by IETF Requests for Comments (RFC) and working
`groups[7] and increasingly by style guides.[8][9] This spelling also appears in most dictionaries.[10][11][12][13][14][15][16]
`e-mail is the format that sometimes appears in edited, published American English and British English writing as
`reflected in the Corpus of Contemporary American English data,[17] but is falling out of favor in some style
`guides.[9][18]
`mail was the form used in the original protocol standard, RFC 524.[19] The service is referred to as mail, and a single
`piece of electronic mail is called a message.[20][21]
`EMail is a traditional form that has been used in RFCs for the "Author's Address"[20][21] and is expressly required "for
`historical reasons".[22]
`E-mail is sometimes used, capitalizing the initial E as in similar abbreviations like E-piano, E-guitar, A-bomb, and H-
`bomb.[23]
`An Internet e-mail consists[24] of an envelope and content; the content in turn consists[25] of a header and a body.
`
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`Origin
`
`Email - Wikipedia
`
`Computer-based mail and messaging became possible with the advent of time-sharing computers in the early 1960s, and
`informal methods of using shared files to pass messages were soon expanded into the first mail systems. Most developers
`of early mainframes and minicomputers developed similar, but generally incompatible, mail applications. Over time, a
`complex web of gateways and routing systems linked many of them. Many US universities were part of the ARPANET
`(created in the late-1960s), which aimed at software portability between its systems. That portability helped make the
`Simple Mail Transfer Protocol (SMTP) increasingly influential.
`
`For a time in the late 1980s and early 1990s, it seemed likely that either a proprietary commercial system or the X.400
`email system, part of the Government Open Systems Interconnection Profile (GOSIP), would predominate. However, once
`the final restrictions on carrying commercial traffic over the Internet ended in 1995,[26][27] a combination of factors made
`the current Internet suite of SMTP, POP3 and IMAP email protocols the standard.
`
`Operation
`The diagram to the right shows a typical sequence of events[28] that takes place when sender Alice transmits a message
`using a mail user agent (MUA) addressed to the email address of the recipient.
`
`1. The MUA formats the message in email format and uses the submission
`protocol, a profile of the Simple Mail Transfer Protocol (SMTP), to send
`the message content to the local mail submission agent (MSA), in this
`case smtp.a.org.
`2. The MSA determines the destination address provided in the SMTP
`protocol (not from the message header), in this case bob@b.org. The part
`before the @ sign is the local part of the address, often the username of
`the recipient, and the part after the @ sign is a domain name. The MSA
`resolves a domain name to determine the fully qualified domain name of
`the mail server in the Domain Name System (DNS).
`3. The DNS server for the domain b.org (ns.b.org) responds with any MX
`records listing the mail exchange servers for that domain, in this case
`mx.b.org, a message transfer agent (MTA) server run by the recipient's
`ISP.[29]
`4. smtp.a.org sends the message to mx.b.org using SMTP. This server may need to forward the message to other MTAs
`before the message reaches the final message delivery agent (MDA).
`5. The MDA delivers it to the mailbox of user bob.
`6. Bob's MUA picks up the message using either the Post Office Protocol (POP3) or the Internet Message Access
`Protocol (IMAP).
`In addition to this example, alternatives and complications exist in the email system:
`
`Email operation
`
`Alice or Bob may use a client connected to a corporate email system, such as IBM Lotus Notes or Microsoft
`Exchange. These systems often have their own internal email format and their clients typically communicate with the
`email server using a vendor-specific, proprietary protocol. The server sends or receives email via the Internet through
`the product's Internet mail gateway which also does any necessary reformatting. If Alice and Bob work for the same
`company, the entire transaction may happen completely within a single corporate email system.
`Alice may not have a MUA on her computer but instead may connect to a webmail service.
`Alice's computer may run its own MTA, so avoiding the transfer at step 1.
`Bob may pick up his email in many ways, for example logging into mx.b.org and reading it directly, or by using a
`webmail service.
`Domains usually have several mail exchange servers so that they can continue to accept mail even if the primary is
`not available.
`
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`Many MTAs used to accept messages for any recipient on the Internet and do their best to deliver them. Such MTAs are
`called open mail relays. This was very important in the early days of the Internet when network connections were
`unreliable.[30][31] However, this mechanism proved to be exploitable by originators of unsolicited bulk email and as a
`consequence open mail relays have become rare,[32] and many MTAs do not accept messages from open mail relays.
`
`Message format
`
`The Internet email message format is now defined by RFC 5322, with encoding of non-ASCII data and multimedia content
`attachments being defined in RFC 2045 through RFC 2049, collectively called Multipurpose Internet Mail Extensions or
`MIME. RFC 5322 replaced the earlier RFC 2822 in 2008, and in turn RFC 2822 in 2001 replaced RFC 822 – which had
`been the standard for Internet email for nearly 20 years. Published in 1982, RFC 822 was based on the earlier RFC 733 for
`the ARPANET.[33]
`
`Internet email messages consist of two major sections, the message header and the message body, collectively known as
`content.[34][35] The header is structured into fields such as From, To, CC, Subject, Date, and other information about the
`email. In the process of transporting email messages between systems, SMTP communicates delivery parameters and
`information using message header fields. The body contains the message, as unstructured text, sometimes containing a
`signature block at the end. The header is separated from the body by a blank line.
`
`Message header
`Each message has exactly one header, which is structured into fields. Each field has a name and a value. RFC 5322
`specifies the precise syntax.
`
`Informally, each line of text in the header that begins with a printable character begins a separate field. The field name
`starts in the first character of the line and ends before the separator character ":". The separator is then followed by the
`field value (the "body" of the field). The value is continued onto subsequent lines if those lines have a space or tab as their
`first character. Field names and values are restricted to 7-bit ASCII characters. Some non-ASCII values may be
`represented using MIME encoded words.
`
`Header fields
`Email header fields can be multi-line, and each line should be at most 78 characters long and in no event more than 998
`characters long.[36] Header fields defined by RFC 5322 can only contain US-ASCII characters; for encoding characters in
`other sets, a syntax specified in RFC 2047 can be used.[37] Recently the IETF EAI working group has defined some
`standards track extensions,[38][39] replacing previous experimental extensions, to allow UTF-8 encoded Unicode characters
`to be used within the header. In particular, this allows email addresses to use non-ASCII characters. Such addresses are
`supported by Google and Microsoft products, and promoted by some governments.[40]
`
`The message header must include at least the following fields:[41][42]
`
`From: The email address, and optionally the name of the author(s). In many email clients not changeable except
`through changing account settings.
`Date: The local time and date when the message was written. Like the From: field, many email clients fill this in
`automatically when sending. The recipient's client may then display the time in the format and time zone local to
`them.
`RFC 3864 describes registration procedures for message header fields at the IANA; it provides for permanent (http://ww
`w.iana.org/assignments/message-headers/perm-headers.html) and provisional (http://www.iana.org/assignments/mess
`age-headers/prov-headers.html) field names, including also fields defined for MIME, netnews, and HTTP, and referencing
`
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`relevant RFCs. Common header fields for email include:[43]
`
`Email - Wikipedia
`
`To: The email address(es), and optionally name(s) of the message's recipient(s). Indicates primary recipients (multiple
`allowed), for secondary recipients see Cc: and Bcc: below.
`Subject: A brief summary of the topic of the message. Certain abbreviations are commonly used in the subject,
`including "RE:" and "FW:".
`Cc: Carbon copy; Many email clients will mark email in one's inbox differently depending on whether they are in the
`To: or Cc: list. (Bcc: Blind carbon copy; addresses are usually only specified during SMTP delivery, and not usually
`listed in the message header.)
`Content-Type: Information about how the message is to be displayed, usually a MIME type.
`Precedence: commonly with values "bulk", "junk", or "list"; used to indicate that automated "vacation" or "out of office"
`responses should not be returned for this mail, e.g. to prevent vacation notices from being sent to all other
`subscribers of a mailing list. Sendmail uses this field to affect prioritization of queued email, with "Precedence:
`special-delivery" messages delivered sooner. With modern high-bandwidth networks, delivery priority is less of an
`issue than it once was. Microsoft Exchange respects a fine-grained automatic response suppression mechanism, the
`X-Auto-Response-Suppress field.[44]
`Message-ID: Also an automatically generated field; used to prevent multiple delivery and for reference in In-Reply-To:
`(see below).
`In-Reply-To: Message-ID of the message that this is a reply to. Used to link related messages together. This field only
`applies for reply messages.
`References: Message-ID of the message that this is a reply to, and the message-id of the message the previous reply
`was a reply to, etc.
`Reply-To: Address that should be used to reply to the message.
`Sender: Address of the actual sender acting on behalf of the author listed in the From: field (secretary, list manager,
`etc.).
`Archived-At: A direct link to the archived form of an individual email message.
`Note that the To: field is not necessarily related to the addresses to which the message is delivered. The actual delivery list
`is supplied separately to the transport protocol, SMTP, which may or may not originally have been extracted from the
`header content. The "To:" field is similar to the addressing at the top of a conventional letter which is delivered according
`to the address on the outer envelope. In the same way, the "From:" field does not have to be the real sender of the email
`message. Some mail servers apply email authentication systems to messages being relayed. Data pertaining to server's
`activity is also part of the header, as defined below.
`
`SMTP defines the trace information of a message, which is also saved in the header using the following two fields:[45]
`
`Received: when an SMTP server accepts a message it inserts this trace record at the top of the header (last to first).
`Return-Path: when the delivery SMTP server makes the final delivery of a message, it inserts this field at the top of
`the header.
`Other fields that are added on top of the header by the receiving server may be called trace fields, in a broader sense.[46]
`
`Authentication-Results: when a server carries out authentication checks, it can save the results in this field for
`consumption by downstream agents.[47]
`Received-SPF: stores results of SPF checks in more detail than Authentication-Results.[48]
`Auto-Submitted: is used to mark automatically generated messages.[49]
`VBR-Info: claims VBR whitelisting[50]
`
`Message body
`
`Content encoding
`
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`Internet email was originally designed for 7-bit ASCII.[51] Most email software is 8-bit clean but must assume it will
`communicate with 7-bit servers and mail readers. The MIME standard introduced character set specifiers and two content
`transfer encodings to enable transmission of non-ASCII data: quoted printable for mostly 7-bit content with a few
`characters outside that range and base64 for arbitrary binary data. The 8BITMIME and BINARY extensions were
`introduced to allow transmission of mail without the need for these encodings, but many mail transport agents still do not
`support them fully. In some countries, several encoding schemes coexist; as the result, by default, the message in a non-
`Latin alphabet language appears in non-readable form (the only exception is coincidence, when the sender and receiver
`use the same encoding scheme). Therefore, for international character sets, Unicode is growing in popularity.
`
`Plain text and HTML
`Most modern graphic email clients allow the use of either plain text or HTML for the message body at the option of the
`user. HTML email messages often include an automatically generated plain text copy as well, for compatibility reasons.
`Advantages of HTML include the ability to include in-line links and images, set apart previous messages in block quotes,
`wrap naturally on any display, use emphasis such as underlines and italics, and change font styles. Disadvantages include
`the increased size of the email, privacy concerns about web bugs, abuse of HTML email as a vector for phishing attacks
`and the spread of malicious software.[52]
`
`Some web-based mailing lists recommend that all posts be made in plain-text, with 72 or 80 characters per line[53][54] for
`all the above reasons, but also because they have a significant number of readers using text-based email clients such as
`Mutt. Some Microsoft email clients allow rich formatting using their proprietary Rich Text Format (RTF), but this should
`be avoided unless the recipient is guaranteed to have a compatible email client.[55]
`
`Servers and client applications
`
`Messages are exchanged between hosts using the Simple Mail Transfer
`Protocol with software programs called mail transfer agents (MTAs); and
`delivered to a mail store by programs called mail delivery agents (MDAs, also
`sometimes called local delivery agents, LDAs). Accepting a message obliges an
`MTA to deliver it,[56] and when a message cannot be delivered, that MTA must
`send a bounce message back to the sender, indicating the problem.
`
`Users can retrieve their messages from servers using standard protocols such
`as POP or IMAP, or, as is more likely in a large corporate environment, with a
`proprietary protocol specific to Novell Groupwise, Lotus Notes or Microsoft
`Exchange Servers. Programs used by users for retrieving, reading, and
`managing email are called mail user agents (MUAs).
`
`The interface of an email client,
`Thunderbird.
`
`Mail can be stored on the client, on the server side, or in both places. Standard formats for mailboxes include Maildir and
`mbox. Several prominent email clients use their own proprietary format and require conversion software to transfer email
`between them. Server-side storage is often in a proprietary format but since access is through a standard protocol such as
`IMAP, moving email from one server to another can be done with any MUA supporting the protocol.
`
`Many current email users do not run MTA, MDA or MUA programs themselves, but use a web-based email platform, such
`as Gmail, Hotmail, or Yahoo! Mail, that performs the same tasks.[57] Such webmail interfaces allow users to access their
`mail with any standard web browser, from any computer, rather than relying on an email client.
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`Filename extensions
`Upon reception of email messages, email client applications save messages in operating system files in the file system.
`Some clients save individual messages as separate files, while others use various database formats, often proprietary, for
`collective storage. A historical standard of storage is the mbox format. The specific format used is often indicated by
`special filename extensions:
`
`Email - Wikipedia
`
`eml
`
`emlx
`
`msg
`
`mbx
`
`Used by many email clients including Novell GroupWise, Microsoft Outlook Express, Lotus
`notes, Windows Mail, Mozilla Thunderbird, and Postbox. The files contain the email contents as
`plain text in MIME format, containing the email header and body, including attachments in one
`or more of several formats.
`
`Used by Apple Mail.
`
`Used by Microsoft Office Outlook and OfficeLogic Groupware.
`
`Used by Opera Mail, KMail, and Apple Mail based on the mbox format.
`
`Some applications (like Apple Mail) leave attachments encoded in messages for searching while also saving separate
`copies of the attachments. Others separate attachments from messages and save them in a specific directory.
`
`URI scheme mailto
`The URI scheme, as registered with the IANA, defines the mailto: scheme for SMTP email addresses. Though its use is
`not strictly defined, URLs of this form are intended to be used to open the new message window of the user's mail client
`when the URL is activated, with the address as defined by the URL in the To: field.[58]
`
`Types
`
`Web-based email
`Many email providers have a web-based email client (e.g. AOL Mail, Gmail, Outlook.com, Hotmail and Yahoo! Mail). This
`allows users to log into the email account by using any compatible web browser to send and receive their email. Mail is
`typically not downloaded to the client, so can't be read without a current Internet connection.
`
`POP3 email services
`The Post Office Protocol 3 (POP3) is a mail access protocol used by a client application to read messages from the mail
`server. Received messages are often deleted from the server. POP supports simple download-and-delete requirements for
`access to remote mailboxes (termed maildrop in the POP RFC's).[59]
`
`IMAP email servers
`The Internet Message Access Protocol (IMAP) provides features to manage a mailbox from multiple devices. Small
`portable devices like smartphones are increasingly used to check email while travelling, and to make brief replies, larger
`devices with better keyboard access being used to reply at greater length. IMAP shows the headers of messages, the sender
`and the subject and the device needs to request to download specific messages. Usually mail is left in folders in the mail
`server.
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`MAPI email servers
`Messaging Application Programming Interface (MAPI) is used by Microsoft Outlook to communicate to Microsoft
`Exchange Server - and to a range of other email server products such as Axigen Mail Server, Kerio Connect, Scalix,
`Zimbra, HP OpenMail, IBM Lotus Notes, Zarafa, and Bynari where vendors have added MAPI support to allow their
`products to be accessed directly via Outlook.
`
`Email - Wikipedia
`
`Uses
`
`Business and organizational use
`Email has been widely accepted by business, governments and non-governmental organizations in the developed world,
`and it is one of the key parts of an 'e-revolution' in workplace communication (with the other key plank being widespread
`adoption of highspeed Internet). A sponsored 2010 study on workplace communication found 83% of U.S. knowledge
`workers felt email was critical to their success and productivity at work.[60]
`
`It has some key benefits to business and other organizations, including:
`
`Facilitating logistics
`Much of the business world relies on communications between people who are not physically in
`the same building, area, or even country; setting up and attending an in-person meeting,
`telephone call, or conference call can be inconvenient, time-consuming, and costly. Email
`provides a method of exchanging information between two or more people with no set-up costs
`and that is generally far less expensive than a physical meeting or phone call.
`Helping with synchronisation
`With real time communication by meetings or phone calls, participants must work on the same
`schedule, and each participant must spend the same amount of time in the meeting or call.
`Email allows asynchrony: each participant may control their schedule independently.
`Reducing cost
`Sending an email is much less expensive than sending postal mail, or long distance telephone
`calls, telex or telegrams.
`Increasing speed
`Much faster than most of the alternatives.
`Creating a "written" record
`Unlike a telephone or in-person conversation, email by its nature creates a detailed written
`record of the communication, the identity of the sender(s) and recipient(s) and the date and time
`the message was sent. In the event of a contract or legal dispute, saved emails can be used to
`prove that an individual was advised of certain issues, as each email has the date and time
`recorded on it.
`
`Email marketing
`Email marketing via "opt-in" is often successfully used to send special sales offerings and new product information.[61]
`Depending on the recipient's culture,[62] email sent without permission—such as an "opt-in"—is likely to be viewed as
`unwelcome "email spam".
`
`Personal use
`
`Personal computer
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`Many users access their personal email from friends and family members using a personal computer in their house or
`apartment.
`
`Mobile
`Email has become used on smartphones and on all types of computers. Mobile "apps" for email increase accessibility to
`the medium for users who are out of their home. While in the earliest years of email, users could only access email on
`desktop computers, in the 2010s, it is possible for users to check their email when they are away from home, whether they
`are across town or across the world. Alerts can also be sent to the smartphone or other device to notify them immediately
`of new messages. This has given email the ability to be used for more frequent communication between users and allowed
`them to check their email and write messages throughout the day. As of 2011, there were approximately 1.4 billion email
`users worldwide and 50 billion non-spam emails that were sent daily.[63]
`
`Individuals often check email on smartphones for both personal and work-related messages. It was found that US adults
`check their email more than they browse the web or check their Facebook accounts, making email the most popular
`activity for users to do on their smartphones. 78% of the respondents in the study revealed that they check their email on
`their phone.[64] It was also found that 30% of consumers use only their smartphone to check their email, and 91% were
`likely to check their email at least once per day on their smartphone. However, the percentage of consumers using email
`on smartphone ranges and differs dramatically across different countries. For example, in comparison to 75% of those
`consumers in the US who used it, only 17% in India did.[65]
`
`Declining use among young people
`As of 2010, the number of Americans visiting email web sites had fallen 6 percent after peaking in November 2009. For
`persons 12 to 17, the number was down 18 percent. Young people preferred instant messaging, texting and social media,
`and email was not designed for them anyway. Technology writer Matt Richtel said in The New York Times that email was
`like the VCR, vinyl records and film cameras--no longer cool and something older people do.[66][67]
`
`A 2015 survey of Android users showed that persons 13 to 24 used messaging apps 3.5 times as much as those over 45, and
`were far less likely to use email.[68]
`
`Issues
`
`Attachment size limitation
`Email messages may have one or more attachments, which are additional files that are appended to the email. Typical
`attachments include Microsoft Word documents, pdf documents and scanned images of paper documents. In principle
`there is no technical restriction on the size or number of attachments, but in practice email clients, servers and Internet
`service providers implement various limitations on the size of files, or complete email - typically to 25MB or less.[69][70][71]
`Furthermore, due to technical reasons, attachment sizes as seen by these transport systems can differ to what the user
`sees,[72] which can be confusing to senders when trying to assess whether they can safely send a file by email. Where larger
`files need to be shared, file hosting services of various sorts are available; and generally suggested.[73][74] Some large files,
`such as digital photos, color presentations and video or music files are too large for some email systems.[75]
`
`Information overload
`
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`The ubiquity of email for knowledge workers and "white collar" employees has led to concerns that recipients face an
`"information overload" in dealing with increasing volumes of email.[76][77] With the growth in mobile devices, by default
`employees may also receive work-related emails outside of their working day. This can lead to increased stress, decreased
`satisfaction with work, and some observers even argue it could have a significant negative economic effect,[78] as efforts to
`read the many emails could reduce productivity.
`
`Spam
`Email "spam" is the term used to describe unsolicited bulk email. The low cost of sending such email meant that by 2003
`up to 30% of total email traffic was already spam.[79][80][81] and was threatening the usefulness of email as a practical tool.
`The US CAN-SPAM Act of 2003 and similar laws elsewhere[82] had some impact, and a number of effective anti-spam
`techniques now largely mitigate the impact of spam by filtering or rejecting it for most users,[83] but the volume sent is still
`very high—and increasingly consists not of advertisements for products, but malicious content or links.[84]
`
`Malware
`A range of malicious email types exist. These range from various types of email scams, including "social engineering"
`scams such as advance-fee scam "Nigerian letters", to phishing, email bombardment and email worms.
`
`Email spoofing
`Email spoofing occurs when the email message header is designed to make the message appear to come from a known or
`trusted source. Email spam and phishing methods typically use spoofing to mislead the recipient about the true message
`origin. Email spoofing may be done as a prank, or as part of a criminal effort to defraud an individual or organization. An
`example of a potentially fraudulent email spoofing is if an individual creates an email which appears to be an invoice from
`a major company, and then sends it to one or more recipients. In some cases, these fraudulent emails incorporate the logo
`of the purported organization and even the email address may appear legitimate.
`
`Email bombing
`Email bombing is the intentional sending of large volumes of messages to a target address. The overloading of the target
`email address can render it unusable and can even cause the mail server to crash.
`
`Privacy concerns
`Today it can be important to distinguish between Internet and internal email systems. Internet email may travel and be
`stored on networks and computers without the sender's or the recipient's control. During the transit time it is possible that
`third parties read or even modify the content. Internal mail systems, in which the information never leaves the
`organizational network, may be more secure, although information technology personnel and others whose function may
`involve monitoring or managing may be accessing the email of other employees.
`
`Email privacy, without some security precautions, can be compromised because:
`
`email messages are generally not encrypted.
`email messages have to go through intermediate computers before reaching their destination, meaning it is relatively
`easy for others to intercept and read messages.
`many Internet Service Providers (ISP) store copies of email messages on their mail servers before they are delivered.
`The backups of these can remain for up to several months on their server, despite deletion from the mailbox.
`
`https://en.wikipedia.org/wiki/Email
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`10/19
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`Petitioners Exhibit 1017 - Page 10
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`Email - Wikipedia
`5/10/2018
`the "Received:"-fields and other information in the email can often identify the sender, preventing anonymous
`communication.
`web bugs invisibly embedded in email content can alert the sender of any email whenever an email is read, or re-
`read, and from which IP address. It can also reveal whether an email was read on a smartphone or a PC, or Apple
`Mac device via the user agent string.
`There are cryptography applications that can serve as a remedy to one or more of the above. For example, Virtual Private
`Networks or the Tor anonymity network can be used to encrypt traffic from the user machine to a safer network while
`GPG, PGP, SMEmail,[85] or S/MIME can be used for end-to-end message encryption, and SMTP STARTTLS or SMTP over
`Transport Layer Security/Secure Sockets Layer can be used to encrypt communications for a single mail hop between the
`SMTP client and the SMTP server.
`
`Additionally, many mail user agents do not protect logins and passwords, making them easy to intercept by an attacker.
`Encrypted authentication schemes such as SASL prevent this. Fina