I have a setup with Exchange running a important test environment using DomainA.co.uk This is used for internal testing and email works fine internally, but mail flow in/out of the domain has never been setup, also I haven't got ownership of an external DNS running this domain.
I now need to get it working so I can send/receive email externally using DomainB.co.uk, whilst not breaking the working internal mail using DomainA.co.uk
I am familiar with DNS and to an extent Certificates however I'm not sure how to configure the certificate and server so I don't break the internal mail flow, whilst allowing staff to send/receive using domain B externally.
They want to have the exchange server referred too as Mail.domainB.co.uk. Do I need to change anything on the exchange server or just create a Cname in the external DNS pointing to the external IP of server?
Can I setup a SAN cert with both domains? If so how?