Outlook and Outlook Express attachment problem

[jmccall]

I'm having a problem with Outlook and Outlook Express and attachments. The problem is occuring on several machines on the same network. When sending attachments from either mail app and attaching large files > 700Kb the e-mail with attachments are arriving without MIME headers and cannot be decoded by the recipient. They are also missing the subject and body of the e-mail.

In-bound messages with large attachments are not a problem only out-bound. Encoding failure occurs both in plain text and Rich Text/HTML This is a recent problem that began occuring last week. Machines have Norton Internet Security and report no virus\spyware issues. I've also scanned with ad-aware and Spybot S&D. Operating systems are both W2K and WinXP. I've tested with Eudora and there are no problems so I can rule out ISP issues.
It seems to be a problem with the Microsoft Encoding engine that is probably common to both Outlook and Outlook Express but not Eudora.
Any ideas on how I can repair the encoding engine.

 

[jmccall]

In case anyone else has the same problem that I posted here I've been able to resolve the issue. The network uses Winproxy as it's proxy server/firewall, the Winproxy also scans e-mails inbound and outbound (SMTP) for viruses. THe problem is caused by the outbound SMTP scanning, once that was turned off the problem went away. It was odd that using another e-mail client (Eudora) did not cause the encoding problem, only the Outlook or Outlook Express client.