I have set the server to sent notification emails (like for updates available, servers created, etc ) from myserver@domainABC.com .
I added domainABC.com to the server, everything configured (DKIM, spf, etc).
On the domainABC.com virtual server , I configured it to forward to my_addresse@gmail.com
Since this is controllable I’d suggest you set up a server so that you have some idea of the time to search in the logs and see what you come up with.
Mail
Webmin
For starters.
Webmin has it’s own section.
in that webmin action log , I do see the action “email sent to my_addresse@gmail.com” module “Read User Mail”, but I did not received it on my gmail , not in spam, anywhere