Office365 and Winmail.dat Problem Resolved

Office365 offers many great features but has a few flaws that can drive users crazy.  One is encapsulating email in a format the Apple’s products can’t read.  If a recipient calls to complain that they can’t read their attachment and that attachment is labelled winmail.dat, you have this problem.  The first thing to try is to ensure the outgoing email format is plain text or html. Using RTF will cause this problem.  If it happens even when HTML is the selected format, then it’s time to dig into Powershell and tell Office365 to never use encapsulation.

Here are the commands to issue (as an admin) from Powershell to turn off TNEF:

 

$UserCredential = Get-Credential

$Session = New-PSSession -ConfigurationName Microsoft.Exchange -ConnectionUri https://outlook.office365.com/powershell-liveid/ -Credential $UserCredential -Authentication Basic -AllowRedirection

Import-PSSession $Session

Set-RemoteDomain Default -TNEFEnabled $false

To Confirm:
Get-RemoteDomain |fl