Troubleshooting Microsoft Exchange: Opening winmail.dat files on your Mac

Many times when receiving mail attachments with the new Exchange-enabled Microsoft Entourage v.X from Windows users, you will get a winmail.dat file that is inaccessible under Mac OS X. Alan Sill offers a workaround that works well for files extracted from mail via "Save to Downloads Directory" from within Mail:

First you must download and install both libytnef and ytnef from the http://ytnef.sourceforge.net downloads directory and install them. You can install the two pieces of software with the following Terminal commands:

• autoconf
• ./configure
• make

and then:

• sudo make install

in each of the libytnef-1.0

Using the OnMyCommandCM contextual menu utility and its associated editor (freeware), available at: http://free.abracode.com/cmworkshop/, you can also define a contextual menu for the SourceForge tools as follows:

• Command Name:
• Unpack with ytnef to Desktop
• Command:
• /usr/local/bin/ytnef -f ~/Desktop __OBJ_PATH__
• Location:
• First level
• Activation Mode:
• File
• Execution Mode:
• Silent (popen)

Note the above assumes that ytnef has been installed in /usr/loca/bin by compiling and installing both libytnef and ytnef 2.0 as usual.

UPDATE: A few MacFixIt readers suggest TNEF's Enough, a freeware tool developed by Josh Jacob that allows Macs to read and extract files from Microsoft TNEF stream ("winmail.dat") files. Jacob's site also lists a technical explanation for the problems caused by these files:

"The file is a rich text (or MAPI) message that is sent from Outlook to Exchange. When Exchange sends the message to an outside server it writes the MAPI message as a MIME attachment. The unfortunate side effect of this plan is if the Outlook user has someone in their address book as a person who can receive 'Rich Text' then the user will receive the TNEF file whether the user uses Outlook or not."

Feedback? Late-breakers@macfixit.com.

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