When I receive messages with attachments from external mail servers, the attached file size is incorrect. I'm running Exchange 2003 locally. The problem seems to be happening at the SMTP server (the standard MS SMTP server).
I send a 9MB file to a Gmail account. The Exchange message tracking log reports a ~9MB message, but the SMTP server log reports a ~12MB message. Gmail receives the message and reports the attachment correctly as 9MB.
If I forward that same message back to myself from Gmail, the SMTP server reports it coming in as ~12MB, the Exchange log reports it as ~12MB, and in Outlook, the attachment size is reported as 12MB. When I save the attachment, the file on disk is the correct 9MB. No file corruption.
I send a message directly from Gmail to my local account with a file attached.
Original File Size: 9,961,472 bytes SMTP Server Log: 13,630,172 bytes Exchange Log: 13,630,168 bytes Attachment Size Reported By OutlooK: 13MB Size of file after saving to disk from Outlook: 9,961,472 bytes
As you can see, the file size "changes" somehow when it is received by the SMTP service, but the attached file saves correctly as the original size.
I have an ISA 2004 server in front of Exchange, and SMTP filtering is enabled. I also have ESET NOD32 for Exchange running.
At this point I'm not sure where to look. Has anyone seen this before?