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goose
Asked: 2010-12-03 10:51:47 +0800 CST

postfix concurrency limit with round robin dns

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Take the following internal round robin dns setup

mymta.com. IN A 172.31.1.1
mymta.com. IN A 172.31.1.2
mymta.com. IN A 172.31.1.3
mymta.com. IN A 172.31.1.4
mymta.com. IN A 172.31.1.5
mymta.com. IN A 172.31.1.6
mymta.com. IN A 172.31.1.7
mymta.com. IN A 172.31.1.8
mymta.com. IN A 172.31.1.9
mymta.com. IN A 172.31.1.10

Now assume the following postfix setup (assume these are the only tweaks from defaults in debian package)

main.cf:

smtp_connection_cache_destinations = mymta.com
smtp_connection_cache_reuse_limit = 750
smtp_destination_concurrency_limit = 75

transport

* :[mymta.com]

I would expect 75 concurrent connections spread across the 10 A records I've set in DNS. However I'm seeing more than a few hundred connections to mymta.com and I'm wondering if Postfix is "smart" enough to set up 75 concurrent connections for each IP address.

Thoughts?

domain-name-system cache postfix email-server concurrency

1 Answers

  1. You should read this: http://www.postfix.org/TUNING_README.html (Tuning the number of simultaneous deliveries)

    and also understanding how resolver work in Linux might help to avoid such "solutions" in the future ;)

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