Email Content Transfer Encoding

 Posted admin

Many email clients now offer some support for Unicode. Film kabhi alvida naa kehna. While some use Unicode by default,[1] many others will automatically choose between a legacy encoding and Unicode depending on the mail's content, either automatically[2] or when the user requests it.[3]

Technical requirements for sending of messages containing non-ASCII characters by email include

  • encoding of certain header fields (subject, sender’s and recipient’s names, sender’s organization and reply-to name) and, optionally, body in a content-transfer encoding
  • encoding of non-ASCII characters in one of the Unicode transforms
  • negotiating the use of UTF-8 encoding in email addresses and reply codes (SMTPUTF8)
  • sending the information about the content-transfer encoding and the Unicode transform used so that the message can be correctly displayed by the recipient (see Mojibake).

Any emails originating from the Droid to an external (non-corporate) address fail to be delivered, getting 'The format of the Content-Transfer-Encoding 'utf-8' is unknown'. It doesn't seem to matter what the external address is (we've tried emails to Verizon, Gmail, and Yahoo), they all fail. Details of the Base64 encoding Base64 is a generic term for a number of similar encoding schemes that encode binary data by treating it numerically and translating it into a base 64 representation. The Base64 term originates from a specific MIME content transfer encoding.

If the sender’s or recipient’s email address contains non-ASCII characters, sending of a message requires also encoding of these to a format that can be understood by mail servers.

Unicode support in protocols[edit]

  • RFC 6531 provides a mechanism for allowing non-ASCII email addresses encoded as UTF-8 in an SMTP[4] or LMTP protocol

Unicode support in message header[edit]

To use Unicode in certain email header fields, e.g. subject lines, sender and recipient names, the Unicode text has to be encoded using a MIME 'Encoded-Word' with a Unicode encoding as the charset. To use Unicode in domain part of email addresses, IDNA encoding must traditionally be used. Alternatively, SMTPUTF8[4] allows the use of UTF-8 encoding in email addresses (both in a local part and in domain name) as well as in a mail header section. Various standards had been created to retrofit the handling of non-ASCII data to the originally ASCII-only email protocol:

Igcse business studies notes. It can help you to cover all the topics in the quickest way.

  • RFC 2047 provides support for encoding non-ASCII values such as real names and subject lines in email header[5]
  • RFC 5890 provides support for encoding non-ASCII domain names in the Domain Name System[6]
  • RFC 6532 allows the use of UTF-8 in a mail header section [7]

Unicode support in message bodies[edit]

As with all encodings apart from US-ASCII, when using Unicode text in email, MIME must be used to specify that a Unicode transformation format is being used for the text.

UTF-7, although sometimes considered deprecated, has an advantage over other Unicode encodings in that it does not require a transfer encoding to fit within the seven-bit limits of many[quantify] legacy Internet mail servers. On the other hand, UTF-16 must be transfer encoded to fit SMTP data format. Although not strictly required, UTF-8 is usually also transfer encoded to avoid problems across seven-bit mail servers. MIME transfer encoding of UTF-8 makes it either unreadable as a plain text (in the case of base64) or, for some languages and types of text, heavily size inefficient (in the case of quoted-printable).

Some document formats, such as HTML, PostScript and Rich Text Format have their own 7-bit encoding schemes for non-ASCII characters and can thus be sent without using any special email encodings. E.g. HTML email can use HTML entities to use characters from anywhere in Unicode even if the HTML source text for the email is in a legacy encoding (e.g. 7-bit ASCII). For details of this see Unicode and HTML.

See also[edit]

References[edit]

  1. ^https://support.google.com/mail/answer/22841?hl=en
  2. ^'wanderlust/apel'. GitHub. Retrieved 2018-09-05.
  3. ^'Setting Outlook to Use UTF-8'. Retrieved 2018-09-05.
  4. ^ abJiankang, Yao,; Wei, Mao,. 'SMTP Extension for Internationalized Email'. tools.ietf.org. Retrieved 2018-09-05.
  5. ^'MIME (Multipurpose Internet Mail Extensions) Part Three: Message Header Extensions for Non-ASCII Text'. tools.ietf.org. Retrieved 2018-09-05. first= missing last= (help)
  6. ^'Internationalized Domain Names for Applications (IDNA): Definitions and Document Framework'. tools.ietf.org. Retrieved 2018-09-05. first= missing last= (help)
  7. ^Abel, Yang,; Shawn, Steele,. 'Internationalized Email Headers'. tools.ietf.org. Retrieved 2018-09-05.

External links[edit]

Retrieved from 'https://en.wikipedia.org/w/index.php?title=Unicode_and_email&oldid=865200802'
  • Status:Closed(View Workflow)
  • Resolution: Fixed
  • Fix Version/s:3.9.0
  • Labels:
  • Symptom Severity:
  • Bug Fix Policy:

Summary of Issue

When JIRA Service Desk Mail Handler processes an email where the body of the email is encoded as Content-Transfer-Encoding: base64:

  1. For a new ticket - the decoded contents are added into Ticket Description (but HTML is also added as an attachment to the ticket)
  2. For an existing ticket - the decoded contents are added into Ticket Comment (but HTML is also added as an attachment to the ticket)

The behaviour works as expected (no additional attachment) when email body is encoded as Content-Transfer-Encoding: quoted-printable.

How to reproduce

  1. Send an email to the JIRA Service Desk listening email address
  2. Once the email has arrived and processed by JIRA Service Desk
    • Extract out the contents of AO_2C4E5C_MAILITEMCHUNK and decode
    • Update the main body encoding from Content-Transfer-Encoding: quoted-printable to Content-Transfer-Encoding: base64
    • Also encode the actual email body to base64
    • Re-encode the whole email as base64
    • Re-update into AO_2C4E5C_MAILITEMCHUNK and set AO_2C4E5C_MAILITEM.status to 'NEW' for reprocessing

Expected Result

Email body updated into Ticket Description / Ticket Comment without adding it again as an attachment.

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Actual Result

Python

In JIRA Service Desk (for both Server and Cloud):

  1. For a new ticket - the decoded contents are added into Ticket Description (but HTML is also added as an attachment to the ticket)
  2. For an existing ticket - the decoded contents are added into Ticket Comment (but HTML is also added as an attachment to the ticket)

Workaround

Email Content Transfer Encoding

There is no usability issue as the comment is posted into the ticket appropriately but the redundant attachment is occupying additional disk space.

The work around would be to simply delete the attachment (which has a random 8 character name such as ohecJTek)

was cloned as

CLOUD-10208Email body encoded as Content-Transfer-Encoding: base64 added as duplicate attachment

  • Open - untriaged
relates to
  • Assignee:
    Unassigned
    Reporter:
    Eric Lam

Email Content-transfer-encoding 7bit

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  • Created:
    Updated:
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