Hello TechNet,

I have an on going situation with winmail.dat attachments. I currently have a ticket open with Microsoft, but I want to see if anyone has personal experience with this. Here is the rundown.

We have migrated from an Exchange 2007 server to Exchange 2013 for the migration to Office 365. We also have a hosted Office 365 server with half of our mailboxes in the cloud and half of them on the Exchange 2013 on premise server.

The current settings for TNEFEnabled:

On Premise: False

Hosted: False

 Whenever a internal email with a calendar invite(exchange calendar, go to meeting) goes out to any external domain the recipients receive winmail.dat.

When settings for TNEFEnabled On Premise and Hosted are set to true both calendar invites and PDF, Excel attachments etc the recipients receive winmail.dat.

When speaking with Microsoft about this issue. The representative was watching me through a LogMeIn session as I set both TNEFEnabled false on both on Premise and Hosted.

This is really frustrating as many employees depend on this to be fully functional, and to be honest am tired of dealing with this.

I need help.

-Ben

Ben

Have you tried:

Turning off Rich Text sending for messages in Microsoft Outlook.

1) Click on Tools

2) Click Options, and then click the Mail Format tab.

3) In the Send in this message format list, select Plain Text, and then click OK.

This will set your default sending method to Plain Text, which will lose your special formatting options with fonts, colors, etc. However everyone, no matter what Email program they are using, will now be able to receive your email with no problems.

Fred,

Thanks for the feedback, but winmail.dat is still being received.

The Mailbox that is still getting Winmail.dat is it On-Premises or in the Cloud?

Fred,

If sending from an on premise mailbox or cloud mailbox the end result is the same. If my old Exchange 2007 server is still online could this be causing confliction. No mailboxes reside on this server, but the server does show in Office 365 with the ability to edit information.

-Ben

If you send Email from a "test mailbox" on the Exchange 2007 On-Premises, still getting the Winmail.dat? 

I could try that. Not sure the connectors are set up correctly for the old On Premise exchange. Are current on premise is Exchange 2013.

-Ben

Well you have a ticket with MS now.

When you were Exchange 2007 On-Premises you did Not have this issue, after going Hybrid with Cloud you Have this issue, point this out and see if they have seen this issue with Hybrid.

I have explained everything to them and I am just waiting for them to come up with something. Figured Id give technet a shot to see if anyone has encountered this personally. Thanks for your input though Fred.

-Ben

does this help?

http://support.microsoft.com/kb/278061/

also have you checked setting on the receivers outlook?

Does this happen to internal addresses?

Does this happen to other / multiple domains/recipients?