Checking emails using Mail Manager

yes, you shout see outbound mails. check your smtp-proxy settings, also check the way how your local mail server can send mails into the internet.

If you use an internal mail server e.g. Exchange for sending e-mails -> you have to config the Sophos UTM internal IP as smarthost there and you have to allow host based relay on the Sophos UTM for your mail server / exchange host. Than you´ll see inbound and outbound mails using Sophos Mail Manager.

regards

Thanks guys but I've now been informed that we are moving to Microsoft 365 and off our Exchange server.

Maybe you should not turn of your onPrem Exchangeserver, see here:

Why you may not be able to decommission on-premises Exchange even with cloud solutions | Born's Tech and Windows World (borncity.com)

Also with O365, you can use your sophos smtp-proxy with hybrid configuration, and yes maybe an cloud smtp-proxy would be a good way, too!

We're currently using a Hybrid set-up and mail from 365 to On-Prem turns up in our Mail Manager but tenant to tenant does not which I find very strange. Is there a reason for this?....Sorry to jump in on this thread... :)

Yes, of course! It worked as designed, mails between tenants/ exchange online users will always routed directly between  exchange online servers

Why? Its easy:

source and targed mailservers are the tenants exchange onlineserver, so why an extra step between it with onpremise? Its the wrong way, if a mail from exchange online server will go trough on premise and than again back to the targed exchange online server.

so, this mails go never trough on premise.

example: in hybrid envoirment, if 2 O365 mailboxuser of same tenant write each other, it will not go trough onpremise exchange.

So can I ask what kind of protection does EOP use for Mail security?

Exchange Online Protection (EOP) overview - Office 365 | Microsoft Docs