Hi there,

I tried to disable OWA signature through ECP console. Unfortunately, it won't work. And how to disable signature on Outlook via GPO?

Regards

Frank 

Either disable signature at the vDir level - https://technet.microsoft.com/en-us/library/bb123515%28v=exchg.150%29.aspx

or with the mailbox policy - https://technet.microsoft.com/en-us/library/dd297989%28v=exchg.150%29.aspx

disable in Outlook using a GPO  http://www.codetwo.com/kb/how-to-disable-adding-signatures-created-in-outlook-for-exchange-users/

Hi,

Please run the following command to check the configuration of signature in owa mailbox policy.

Get-OwaMailboxPolicy | fl Name,SignaturesEnabled

And check if the policy has applied to user mailbox.

Get-CASMailbox <UserName> | fl OwaMailboxPolicy

Best Regards.