This is all I get in mail.log:
Aug 3 12:28:32 localhost ipop3d: pop3 service init from 18.104.22.168
Aug 3 12:28:32 localhost ipop3d: Logout user=??? host=[22.214.171.124]
Debugging info from UebiMiau (via POP):
<- +OK POP3 localhost.localdomain v2003.83 server ready
-> USER opplev.no_even
<- -ERR Unknown AUTHORIZATION state command
And, yeah - I've tried sending to users outside the system. The email is delivered successfully nontheless...