There doesn’t seem to be a clear question or answer on this Discourse so since google’s asking me for logs for STMP and POP for reporting to their Report a delivery problem between your domain and Gmail - Gmail Help form.
If it logs, check /var/logs/mail, etc.
You’re a star @murgero its people like you who make not only this world a better place but forums actually useful. I ended up finding that command buried somewhere deep in someone else’s thread but now this’ll be there for someone else if they end up wanting to know the same thing.
haha no worries:
tail -n20 /var/log/mail to get last 20 lines (change 20 to any number to get that many lines)
A little more help for you.
I’ll take that advice and up you one more with a
tail -n20 /var/log/mail |gist-paste -p to make it instantly shareable.
Never used it before but hell ya!