Hi all,
I have just installed a Sophos XG Firewall (SFOS 17.5.5) as a VM in a small office environment that runs it's own Exchange 2016 server for email.
The XG was set up in MTA mode with an external SSL Certificate as per the documentation. It appeared that all was working, but it soon became apparent that only some of the INCOMING email was making it through to the Exchange Server - no email from Gmail addresses were being delivered. It appears that all other email was being received, but it is difficult to tell if other domains were affected also.
I checked the mail logs and the missing email did not appear at all in the logs, they just never arrived. Gmail senders eventually received a "Delivery incomplete" message.
I change the Sophos XG back to Legacy mode and the Gmail immediately started flowing through into the Exchange Server.
Does anyone have any idea what the problem with MTA mode and Gmail is?
Thanks for any advice you might have.
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