Re: [exim] smarthost and multiple messages per connection

[Alexander Ufimtsev]

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On 2010-03-03 14:04, Lena wrote:
> > By default, exim establishes a separate connection to a remote smtp
> > server, even if this remote server is configured as exim's only smart host.
> > 
> > Since our smarthost does not allow more than 10 connections per minute,
> > it causes significant delays in mail delivery with default configuration.
> 
> Try:
> 
> remote_smtp:
>   driver = smtp
>   serialize_hosts = *
> 

This did not help :-(

I have finally solved the problem though, so I'll answer my own question
in hope that it will be useful for others: it was sufficient to turn off
TLS.

Exim does not work efficiently with TLS due to the nature of its
implementation (process fork for each message delivery). As a result, it
tries to start and stop multiple TLS sessions within the same
unencrypted SMTP: the behaviour that is not precisely described by an
appropriate RFC. If restarting TLS fails, it drops the connection and
re-establishes it, which happened in this case.

More info is here:
http://www.exim.org/exim-html-current/doc/html/spec_html/ch39.html#SECTmulmessam


To turn off TLS, the following had to be added to remote_smtp
(remote_smtp_smarthost in my case) section:

remote_smtp:
   driver = smtp
   hosts_avoid_tls = *



Many thanks,
Alexander

- --
Alexander Ufimtsev
Web Software Developer
School of Computer Science and Informatics
University College Dublin, Belfield, D4, Ireland
T: +353 1 716 2926  F:  +353 1 269 7262


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