[cobalt-security] Random Sendmail attachment mangle query

[Declan Caulfield <declan@xxxxxxxxxx>]

I have a strange ?problem with attachments to emails being randomly
scrambled through our mail server.

I have read up on this topic as much as I can and I understand that Sendmail
or any other MTA, for that matter,  is not concerned with the contents of a
mail envelope, it merely accepts it for delivery. I have checked through the
various MIME encoding issues, ESMTP issues and looked at what the MTU's are
using to create the mail attachment. I have eliminated most of these issues
during my analysis.

Here are the symptoms:
Windoze clients sending mail using Outlook as a MTU use Sendmail, running on
a dedicated Raq3i, for delivery. Mail is processed with no errors of any
kind. Sendmail to Sendmail works 10/10, Sendmail to Exchange generates these
random errors. 

I have read about issues where Sendmail converts some MIME formats such as
QP to Base64 encoding, however, this does not seem to be the issue as the
mail envelope arrives intact to it's destination, the attachment block is
recognised and decoded to the correct 'filename' and yet when opened it is
still encoded to a Base64 or something.

Is this a case of double encoding at some point in the chain of delivery?

It only seems to effect users on Microsoft Outlook who are receiving a file
from our MTA (sendmail).

Should anyone have heard of this problem before I would appreciate some
pointers.

Many thanks.

./Declan

Apologises for the somewhat off the point question to the security list.