I'm having a problem with attachments that I can't seem to fix. When I send attachments to certain people, they receive them as .DAT files. Some of these people are on Macs, some of them are using Outlook as a POP3 mail client, and others are in a corporate environment with an Exchange server. I've tried sending the mail as Plain Text, but that doesn't always work (I compose a new mail, set format to Plain Text, select users and click send). I've even made sure the Internet Format property of the address I'm sending to is set to "Plain Text Only", and some recipients still get .DAT files. I'd like to be able to send HTML formatted email with attachments, but I can't figure out how to do it. I use a lot of plug-ins, so perhaps one of them is the culprit. Any suggestions?

Why do some people receive the winmail.dat file?

Outlook generates and attaches a winmail.dat file at the end of each message that only Outlook can use. It's put at the end of the message so that on the receiving side Outlook can display the message correctly. This file is typically very small, and may or may not include the original attachment. However, Outlook is the only email program that can use this information. Therefore, recipients using email clients other than Outlook might receive the winmail.dat file instead of the original message.

To help prevent email recipients from receiving winmail.dat files the formatting needs to be changed to Plain Text. Below are various ways you can change the formatting on the emails you send, including formatting for individual emails, specific contacts, and for all the email you send.

Changing the formatting for all email sent
This will change the email format for every email you send. First, select Tools->Options from the Outlook menu bar, then select the "Mail Format" tab in the dialog window. In the first drop-down list, under the "Message Format" heading, select Plain Text, and click the "OK" button.

Now, every email you send will be sent in Plain Text.

Changing the format for specific Contacts in Outlook 2003
This will change the email only for specific Contacts. Open Address Book by selecting Tools->Address Book and select the desired recipient's entry in your address book. Double-click on the recipient's email address--another dialog box will appear. Select Plain Text on the Internet Format drop down box and click the "OK" button.

Now, every email you send to this Contact will be sent in Plain Text.