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Re: [OT] email standard maximum line length

On Thu, Apr 03, 2003 at 02:31:09PM -0800, Paul E Condon wrote:
> I am getting email from an old friend who is not a Debian type like
> me.  He types his email into a window on what he calls 'just a
> standard PC' and the computer automatically starts new lines on his
> screen when needed. His software is, in his words, 'just plain mail
> software, nothing special'.  Sometimes his emails are longer than a
> few dozen words, and when they exceed about one thousand characters of
> text, they are truncated. The last part of what he typed is simply
> missing from my copy. I suppose that there is a line buffer somewhere
> in the chain of delivery that is 1000 or 1024 bytes long. 
> I am curious about where in the chain of delivery the truncation might
> be happening. Is there a standard for email that specifies a line
> buffer size?

Yes, there is. RFC 2821 ("Simple Mail Transport Protocol"), section

   text line
      The maximum total length of a text line including the <CRLF> is
      1000 characters (not counting the leading dot duplicated for
      transparency).  This number may be increased by the use of SMTP
      Service Extensions.

RFC 2822 ("Internet Message Format") further notes:

2.1.1. Line Length Limits

   There are two limits that this standard places on the number of
   characters in a line. Each line of characters MUST be no more than
   998 characters, and SHOULD be no more than 78 characters, excluding
   the CRLF.

   The 998 character limit is due to limitations in many implementations
   which send, receive, or store Internet Message Format messages that
   simply cannot handle more than 998 characters on a line. Receiving
   implementations would do well to handle an arbitrarily large number
   of characters in a line for robustness sake. However, there are so
   many implementations which (in compliance with the transport
   requirements of [RFC2821]) do not accept messages containing more
   than 1000 character including the CR and LF per line, it is important
   for implementations not to create such messages.

> My software is fetchmail and mutt. I have already established that the
> truncation is not happening in mutt, because I see it in
> /var/mail/pecondon .  I haven't yet figured out how I might check on
> fetchmail. I don't have access to the internals of my ISP.

It may well be an MTA somewhere along the way.

> I'm working on getting him to press carriage return from time to time
> as he types, but he is somewhat set in his ways.

This problem also implies that his mail user agent is buggy.


Colin Watson                                  [cjwatson@flatline.org.uk]

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