Tag Archives: exim disable ipv6 true

An issue with exim — mails not getting delivered to certain mail-servers

Facing an issue with exim, that it doesn’t send any mails to certain SMTP server’s like gmail etc?

First place to check is the /var/log/exim_mainlog and see if you can spot something like this

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-bash-3.2# grep 1W6OuM-0005cl-J8 /var/log/exim_mainlog
2014-01-23 19:21:42 1W6OuM-0005cl-J8 <= root@host.xxxx. U=root P=local S=350 T=”test mail” for test@gmail.com
2014-01-23 19:21:42 cwd=/var/spool/exim 4 args: /usr/sbin/exim -v -Mc 1W6OuM-0005cl-J8
2014-01-23 19:21:42 1W6OuM-0005cl-J8 gmail-smtp-in.l.google.com [xxxx:abcd:xxxx:xab::xa] Network is unreachable
2014-01-23 19:21:43 1W6OuM-0005cl-J8 Completed

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You can see that exim is trying to send outgoing emails via IPv6 . It happens if the recipient server supports it, ( gmail supports it ) as a result mail delivery gets affected or the mails reach junk/spam folder.

If IPv6 delivery is not intended and DNS records for the same are not configured, then the recipient SMTP server would not be able to obtain a reverse DNS entry of the sending IP ( IP in IPv6 ) and as a result it affects the mail delivery.

To get around this, either configure your IPv6 DNS entries or just force exim to send mails only via IPv4 by adding the below line to the exim config file ( /etc/exim.conf

disable_ipv6 = true

Finally restart exim.