- Connect to Exchange Online by using remote PowerShell. For more information about how to do this, see Connect to Exchange Online Using Remote PowerShell.
- Run the following commands:
$owapolicy = Get-OwaMailboxPolicy
$ owapolicy.AllowedMimeTypes.Remove("text/html")Note It may take as long as 30 minutes for the changes to take effect.
Set-OwaMailboxPolicy -AllowedMimeTypes $owapolicy.AllowedMimeTypes -Identity $owapolicy.Identity
Article ID: 2971787 - Last Review: 20 Dec 2016 - Revision: 1