When out of office mails from our company go to a gmail address, we get this error in return:
May 2 12:59:29 lg-info-mail postfix/smtp: AB34490FD1: to=, relay=gmail-smtp-in.l.google.com[220.127.116.11]:25, delay=0.11, delays=0.01/0/0.1/0, dsn=5.0.0, status=bounced (host gmail-smtp-in.l.google.com[18.104.22.168] said: 550 Requested action not taken: mailbox unavailable (in reply to MAIL FROM command))
My mail has X-Envelope-From and From set.
What does "in reply to MAIL FROM command" means exactly? What is my mail lacking of?