Winmail.dat is an email attachment you normally don’t see. It contains formatting information for RTF (rich-text format) messages sent by Outlook. The system used for this is called TNEF (Transport Neutral Encapsulation Format ) but despite the word ‘neutral’ it’s a proprietary Microsoft format. Because it’s an ‘in-house’ Microsoft format some non-MS email programs can’t convert the incoming message into a fully formatted message – the result is plain text plus a mysterious winmail.dat attachment.
These days RTF formatted messages have been largely replaced by HTML formatting because it’s more widely supported by email software. Outlook has supported HTML formatted emails for the last few versions and is much preferred over the proprietary Microsoft system.
The solution for Jeremy is to check the Outlook settings and make sure all messages are sent in HTML format.
Switching to HTML format
These days even Microsoft recognizes the superiority of HTML formatted messages. The default format is HTML and there’s even an option to convert RTF messages to HTML format when sending to Internet email addresses (as opposed to intra-organization recipients). Go to Tools | Options | Mail Format to see the default message format (should be HTML) then click on the Internet Format to see Outlook Rich Text option to convert messages.
alternativa 1: Microsoft Knowledge Base article 958012 (http://office-watch.com/kb/?958012)
alternativa 2: winmail opener (http://www.eolsoft.com/freeware/winmail_opener/)