Hi, from time to time I receive following error while I try to send an email (normally using Thunderbird or Outlook - not bulk mail) to some Gmail mailbox: subject: Undelivered Mail Returned to Sender (my actual hostname was replaced with similar casrv02.myserver.com) I think it is related to the improper configuration of IPv6. The obvious solution is to disable IPv6 or to do some additional configuration. The problem might also be that my reverse DNS is casrv02.myserver.com while the domain I send out the email from is [email protected] (different from reverse DNS). Can you please help me out how to disable IPv6 or adjust the configuration for ISPConfig? (if that is the issue in your opinion) My setup: Debian 7 x64, OVH VPS Cloud Installed following these howto instructions: The Perfect Server - Debian Wheezy (Apache2, BIND, Dovecot, ISPConfig 3), nothing customized.
The easiest solution is to switch postfix to ipv4 only. Add the following line in the postfix main.cf file and restart postfix: inet_protocols=ipv4 If you like to use ipv6, then you will have to check 2 things: 1) is there a IPv6 recrd (AAAA) for the hostname "casrv02.myserver.com" in the zone "myserver.com" that points to the IPv6 address of your server? 2) Does your IPv6 address has a reverse dns record that points back to the hostname "casrv02.myserver.com". The reverse recod for the IP has most likely to be set in the ovh controlpanel of the server / vm and not in ispconfig.
Thank you till Code: inet_protocols=ipv4 solved the problem for me for good - no more returned emails! Btw. I contacted my ISP (OVH) and they currently provide IPv6 but no reverse DNS record (official reply from OVH support) so this is the only solution for OVH users atm.
