Re: Max length of an email subject line

[Ken Sims <mdrg5003@xxxxxxxxxxx>]

Hi Bob -

> Anybody know what the maximum length of an email's subject line can be?

The subject is an unstructured field so it has no maximum length.

There is a maximum line length of 998 (excluding the trailing CR and LF) 
however the subject can be folded across multiple lines so that is not a 
restriction on the length of the subject itself.

From rfc2822 about unstructured header fields:

   Some field bodies in this standard are defined simply as
   "unstructured" (which is specified below as any US-ASCII characters,
   except for CR and LF) with no further restrictions.  These are
   referred to as unstructured field bodies.  Semantically, unstructured
   field bodies are simply to be treated as a single line of characters
   with no further processing (except for header "folding" and
   "unfolding" as described in section 2.2.3).

See http://www.rfc-editor.org/rfc/rfc2822.txt about email messages
and http://www.rfc-editor.org/rfc/rfc2821.txt about SMTP.

Ken
http://www.kensims.net/
Opinions expressed are my own and do not necessarily represent the views
of my employer or anyone in their right mind.