EXCHANGE   Exchange 2013 – Emails sent in TNEF winmail format



Some users notified me that some external recipients could not open sent attachments.
After some tests I realized that the problem only appeared for external contacts.

When sending this email…
Exchange 2013 TNEF Remote Domain 1

to a contact configured in the Active Directory, the Gmail web client showed this:
Exchange 2013 TNEF Remote Domain 3

The same recipient without existing in Active Directory receives the email correctly:
Exchange 2013 TNEF Remote Domain 2

My users notified that the external recipients couldnt see the images, open an attached PDF…
In this case, the embedded image is showed as an attachment. I suppose it depends on the email client and its compatibility with TNEF email format because the problem is that Exchange 2013 uses this format by default for external contacts.

The KB2487954 shows the method to disable the TNEF format for a specified domain.
In my scenario I wanted to disable it for all external domains, and configuring all of them manually is not an option…

To disable TNEF for all domains:

The "Default" RemoteDomain is not disabled by default:

[PS] C:\> Get-RemoteDomain Default | fl TNEFEnabled
TNEFEnabled : 
[PS] C:\> Set-RemoteDomain Default -TNEFEnabled $false 

[PS] C:\> Get-RemoteDomain Default | fl TNEFEnabled 
TNEFEnabled : False 

This way this annoying problem is solved

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