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People sending winmail.dat

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by toretto84 2 views

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One of our customers has been complaining a lot lately about "attachments" not being received. This only happens when certain people send them mails.

We've taken a log at their Watchguard Firewall every time, and it's always the same problem. We see a mail arrive with "winmail.dat" as attachment; instead of the real attachment.

The problem is that our client DOES use Outlook, so from what I've read it should be able to "interpret" the information in winmail.dat, but they can't. Other people, not a member of our client's domain, are having the same problem, with the same e-mail.

This could be either

a) a very weird problem w/ Outlook of the sender
b) a problem w/ the firewall - I strongly doubt it, because tons of e-mails pass every day, from Outlook users, with all kinds of attachments.

I'm lost here. Is this a problem on the side of our client or on the side of the person sending the e-mail (which, according to MS documentation, isn't the case - they're NEVER wrong)?

5 replies

by itnerdist

Same issue here, also with a watchguard firewall. did you ever resolve?
we are running exchange 2010 and all clients are outlook 2007

by itnerdist

I really appreciate the quick response, i have been looking into this and everywhere i see the resolution seems to be on the sender side. Is this always the case or is there something that i can configure as the receiver of these emails to resolve the problem. again we are ruinning exchange 2010 and all of our clients have outlook 2007. it would make sense that outlook could decode the RTF info but it does not.

by david_frankham

If an Outlook client, or Contact in Exchange is configured to send email in Outlook Rich Text format (Outlook) or "Use MAPI Rich Text Format" (Exchange contact) then the message will have 2 parts - one is the plain text version of the email, and the second it the Rich Text version along with any attachments (encapsulated in TNEF format in a file called winmail.dat).

If the receiving end is a Microsoft email client (Outlook, and maybe Outlook Express, Windows Live mail) then it should be able to decode the TNEF encoded portion of the message and correctly display the Rich Text formatting and any attachements correctly.

If the receiving end is a non Microsoft client, then the plain text version of the message will be displayed with a winmail.dat attachment.

NOTE: If you receive a winmail.dat file in an Outlook client, then it is likely that something has stipped some X- headers out of the SMTP email. I have certainly seen this happen on Watchguard firewalls - they need to allow the following headers through on the SMTP proxy:
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
X-MimeOLE:

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