From: Noel Jones (njonesmegan.vbhcs.org)
Date: Sun Mar 02 2008 - 14:57:29 CST

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Patrick Ben Koetter wrote:
> The Yahoo! guidelines for establishing SMTP connections to Yahoo! Mail require
> a maximum of 5 messages per SMTP connection:
>
> "Are there any guidelines for establishing SMTP connections to Yahoo! Mail?"
> <http://help.yahoo.com/l/us/yahoo/mail/postmaster/postmaster-277515.html>
>
> I know I can use a special default_destination_concurrency_limit to limit the
> number of parallel connections (which is not what I need) and $max_use works
> on incomming connections, but not on outgoing as it seems.
>
> Is there any parameter to control the maximum number of messages per SMTP
> connection?
>
> prick
>

Postfix smtp connection caching is time based (how long can a
connection stay active), not count based, so there is no
control to limit the number of messages per connection to some
arbitrary number.

http://www.postfix.org/postconf.5.html#smtp_connection_cache_on_demand
http://www.postfix.org/postconf.5.html#smtp_connection_cache_time_limit

You can turn off connection caching for a specific transport
in master.cf.

abbreviated example:
# transport
yahoo.com nocache:

# master.cf
nocache unix - - n - - smtp
   -o smtp_connection_cache_on_demand=no

--
Noel Jones

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