While mkryptor (version 2.1+) does include handling for TNEF, it is still recommended to avoid sending messages in this format if possible.
Note: If you are using Microsoft Exchange, message format settings are made at the server level. See the relevant Exchange Set-up Guide for details
Further information on the downside of using TNEF can be found in the following Microsoft Support Article: http://support.microsoft.com/kb/290809
To configure Outlook to use HTML format for messages, follow the below steps:
- In Outlook, go to Tools -> Options
- In the Options window, select the 'Mail Format' tab
- In the drop-down for 'Compose in this message format' select HTML
- Now click the 'Internet Format...' button
- This will open a new window with some important options
- In the Internet Format window, find the section titled 'Outlook Rich Text options'
- In the drop-down box, select 'Convert to HTML format'
- Click OK to save changes and also click OK on the main Options window
- Your messages should now go out in HTML format