Invoice email not working after changed IP address

Hi, I am running ERPNext 6.x locally on VM. I have exported the VM due to a failed server and imported on another server. It worked without any issue. I was planning a version upgrade from 6 to 7. So I have imported VM again on a different server and changed the 1st imported VM IP address. The upgrade was problematic. So I am running on my 1st imported VM. Now I discovered that my outgoing email of invoices is not working. I have enable-scheduler, and restarted the bench. That did not solve the problem. Is there a way to track email activities on frappe-bench? Thank you.

What email service are you using? What is the OS you are running? Did you enable mail relay for your old VM’s IP address? More info would help…

Hi, We have our email server hosted. The version of ERPNext is 6.12, previous configured and worked for the past six month, it was installed as a VM on Xenserver 6.5 pool. A few days ago, there was hardware issue with the server pool. So the VM was exported and reimported on a temporary server. It worked fine. The IP was not changed during all this time.

We decided to try a version upgrade since we were redoing the server pool. After we finished with the Xenserver setup, added a new server into the pool then reimported VM onto the new server. The imported VM worked fine, with the same IP address. We subsequently shut down the VM on the temporary server and changed the IP address /etc/network/interfaces (static). We performed an upgrade on the newly imported VM on the new server, failed. So we went back to the VM that was on the temporary server with changed IP address. Now the email doesn’t work. Can not email invoices etc.

Environment: Ubuntu 14.04.4 lts
ERPnext version: 6.12.3
Bench version: 6.12.2

Email setup has not been changed on the VM, so we don’t have to look into it. The only change was the IP address of the connected network interface. Bench-enable-scheduler (enabled), no task-log files, no scheduler log found, etc. Need some idea of how to trace outgoing emails (notifications)