This is what I get:
<snip>
The mail system
contact@esotericsoftware.com: host aspmx.l.google.com[2404:6800:4008:c03::1b]
said: 550-5.7.1 [2400:8902::f03c:91ff:fe60:2939] Our system has detected
that this 550-5.7.1 message does not meet IPv6 sending guidelines regarding
PTR records 550-5.7.1 and authentication. Please review 550-5.7.1
https://support.google.com/mail/?p=IPv6AuthError for more information 550
5.7.1 . s13si413281plj.719 - gsmtp (in reply to end of DATA command)
</snip>
Can you contact me, please? I have urgent questions about license renewal.
<removed>
All the best,
Sakari
