We have SM 14running as MX Backup server. All was well in that there were usually a few messages in there and some passed through to the main server which then handled the spam checking etc. All domains have a secondary MX set up pointing to the mxbackup server
I know not everyone agrees the need for a backup server but we have found that if the mail server is down it's the a good way to queue email and then send them thru when the server is back online.
recently we placed both servers behind a dedicated firewall and we changed the IP of the main mail server. Whilst we were moving the mail server to its new location, we expected the backup server to start queuing mail. But nothing ever came thru. And it must have been like that since we moved it behind the firewall but never noticed.
In fact, we needed to change the bindings to the new internal IP for all the ports. When I did that the logs started reporting incoming connections. They were all rejected even when the email address was a valid email address on the main server.
I am sure that at one time emails sent to valid users would be sent thru by the mxbackup. It's a spam trap but not a lot gets through.
So I decided to add the smart gateway option and webservices to the incoming gateway record using the main server admin and email and its web address - but that doesn't seem to work either. The logs show 'user does not exist' for valid emails on the main server. This means that if the main server goes down, all mail we be rejected by the back up server? Or does it somehow know it has to queue them?
Any ideas anyone?