Everyone who uses Outlook seems to have had at least one encounter with the not-easily-useable Winmail.dat file, an attachment having the format TNEF (Transport Neutral Encapsulation Format) that is spawned from Microsoft’s Exchange Server when messages are sent using Rich Text Format or RTF. TNEF was created by Microsoft and was intended for Exchange/Outlook systems only. Trouble is that even between two but unrelated Exchange Server systems, Winmail.dat is not straight-forward to manage and is a frequent cause of user frustration. And while there was a time when the RTF format was the go-to method of sharing documents between PC and Mac users, that need has largely evaporated.
If you receive a Winmail.dat file and want to decode it, there are several utilities available to do so. Here are two that are free:
http://www.eolsoft.com/freeware/winmail_opener/
Microsoft provides this link for TNEF, RTF, and winmail.dat information:
http://technet.microsoft.com/en-us/library/bb310786.aspx
Now, if you want to disable sending messages formatted in RTF, there are several levels available to accomplish this:
For the Sender, settings to manage the format of messages are available within most all versions of Outlook. Indeed, the format can be managed on the Sender’s Outlook at the individual Internet recipient level (Open the recipient’s Contact page, double-click the recipient’s email address, and select the Internet Format) or for recipients of all messages. For the latter, in Outlook 2007 & 2010, select the menu items Tools/Options and then the Mail Format Tab. We see HTML, Rich Text, and Plain Text as options for message format.
In Outlook 2013, you must select File/Option and then select Mail in the Outlook Options left pane. In the main or right pane, you’ll see Compose messages in this format like this:
As a Sys Admin, you can manage the ability of users to send RTF formatted messages at the Exchange level, however there are a few issues to consider. For example, if the recipient is to be part of Outlook Voting, that Vote message must be formatted in RTF. So care must be taken when managing settings for Remote Domains on an Exchange Server.
In most situations, external domains are all defined by Name “Default” and a DomainName of “*”. In Exchange 2000, 2003, 2007, and 2010 we can manage sending in RTF in the Exchange GUI. We no longer have any Exchange 2000 or 2003 Servers in service, so the instructions and images that follow only apply to 2007 & 2010:
- Open the Exchange Management Console
- Expand the Organization Configuration
- Select Hub Transport in the left pane
- Select the Remote Domains tab on the right
- Open the Properties page for Default
- Select the Message Format tab
At this point you can choose when or if RTF will be used by the Exchange Server for the specific Remote Domain(s); in this case, we’re talking about all external domains because we selected Default. But if you need a more discriminating approach, other Remote Domain objects can be created.
The game has changed for Exchange 2013 as this and most other settings are all accessed via the Exchange Management Shell. There are a couple of steps to manage RTF settings in Exchange 2013 (this also works in Exchange 2010):
- Open the Exchange Management Shell
- Inspect the current settings where TNEF is enabled with the following command:
Get-RemoteDomain | Where {$_.TNEFEnabled –ne $false}
- In response to this command, you’ll receive a list of External Domain objects that have TNEF enabled. Again, this will generally be a list of one with the Name “Default”
- To disable TNEF for the Remote Domain obeject named Default enter the following:
Set-RemoteDomain –Identity Default –TNEFEnabled $false
Given you applied these settings to the Default object, all messages being sent from the Exchange server and formatted in RTF will be converted to HTML.
