Currently I am experiencing major issues with SPAM or email spoofing rather, and I have spent numerous hours googling potential resolutions to this issue to no avail.
So far I have tried enabling the Sender ID on the edge transport server
creating SPF record for the affected domain
Installed and running GFI mail essentials on the Exchange 2010 server.
Disabled anonymous access/ closing the open relay even though MX toolbox advised that our server wasn't open relay.
I don't know what else I can do with this one and hoping you EE geniuses can assist further.
Any advise, tips on how to combat this spoofing would be greatly appreciated.
Thanks in advance.