Re: [exim] Potential logic error in retry handling for IPv4+…

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Author: Marc Sherman
Date:  
To: exim-users
Subject: Re: [exim] Potential logic error in retry handling for IPv4+IPv6 hosts
Florian Weimer wrote:
> I'm currently facing a mail delivery problem. The sending MTA is Exim
> 4.50. The host has no real IPv6 connectivity, but a working IPv6
> stack, and the DNS resolver returns AAAA records.
>
> Mail to domains which are handled by MX hosts which have both an A and
> AAAA record bounces sporadically with the error message "retry time
> not reached for any host after a long failure period". The
> interesting thing is that the bounce itself gets through, after
> delivery of the original message has failed. "exim -bt" shows that
> Exim gives indeed priority to the AAAA record.
>
> Does this problem sound familiar?


Very familiar. It happened to me in June[0], and we were just
discussing it again earlier this week[1].

[0]
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20050613/msg00002.html
[1]
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20051128/msg00073.html

Philip's conclusion to the second thread[2], just yesterday in fact, was
"do... nothing until somebody else hits a problem." Timing is
everything. :)

[2]
http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20051128/msg00173.html

Anyway, while Philip will probably have some questions for you to help
track down and debug the problem, there is an easy workaround in your
host has no real IPv6 connectivity:

http://www.exim.org/mail-archives/exim-users/Week-of-Mon-20051128/msg00043.html

- Marc