SMTP-Gateway - Inside or outside?

Hello, we use NC in our DMZ. How would you set the SMTP server? From the DMZ to Trust (Exchange) or from DMZ to Untrust (Relay from our provider)? Many thanks. Markus

To be honest, it all depends on your server and your network management.

The “trust” option, depending again, on your mail server configuration is the best way to avoid annoying email Authentication problems and give you more control over SPF, DKIM, and DMARC options.