Hi Bern:

In message
<1467618984.93.0.619589278254.issue2550751@psf.upfronthosting.co.za> ,
Bernhard Reiter writes:
>I wonder if there is a limit on header lines in the standards
>(or in practice). If there is not, it may be a defect gateway software
>which we should call out.

AFAIK there is no standards limit to a header length. Each line is
limited to 1000 characters IIRC. But headers can span multiple lines.
Continuation lines are indented with a space under the header line.

This discussion seems to support my thoughts:

  http://stackoverflow.com/questions/2721605/maximum-size-of-email-x-headers

That being said email -> X gateways, exchange ... may have practical
limitations, but I don't know of any off the top of my head.

My claim is the property header should either be disabled or contain
the full info available to be useful.

>How many file attachments are we talking about anyway?

Potentially it could be unlimited.

>What is the purpose of the header?

It looks like the headers were added by:

  changeset:   3956:bb2722260e47
  user:        Richard Jones <richard@users.sourceforge.net>
  date:        Tue Jan 08 20:55:26 2008 +0000
  files:       CHANGES.txt doc/index.txt roundup/roundupdb.py
  description:
  Fixes from Martin v. L?wis:

  - Messages created through the web are now given an in-reply-to header
    when email out to nosy

  - Nosy messages now include more information about issues (all link
    properties with a "name" attribute)

google for "Martin Löwis x-roundup" points to:

 http://grokbase.com/t/python/tracker-discuss/0817bzj3rw/additional-headers

and that references some issues at:

 Title: add keyword info in emails
 http://psf.upfronthosting.co.za/roundup/meta/issue140

  User want to see if the patch keyword was added to an issue
  so he can filter email.

  Title: Tracker emails should list the classification
  http://psf.upfronthosting.co.za/roundup/meta/issue143

   User wanted the classification so he could filter emails.

   Final comment: This is now fixed in r59861; the tracker
    sends X-Roundup-issue-components, as a comma separated
    list (omitted if there are no components associated with the issue).

Does this answer your question?