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Old 5th March 2011, 00:18
acutchin acutchin is offline
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Default Postfix relayhost and queueing

I have a complex issue with a very simple Postfix configuration. My Postfix server is acting as a relay between a local application server that is generating the email messages and a remote service that ultimately delivers our mail. Like this:

app server -> postfix relay server -> remote smtp server

Mail only flows in this direction, and the postfix server doesn't route, deliver, or accept any other mail. The app server is Java-based, single-threaded, and delivers mail sequentially to the postfix server via SMTP. The remote server requires TLS/SASL.

Mail flows correctly through the Postfix server. The problem is that the app server is experiencing long delays (~.5s) in each SMTP session with the postfix relay server. The administrators of the remote server say they are seeing one complete SMTP session per delivered message from the postfix sever, and they assure us that their system can accept mail much faster than we are sending it. This suggests to me that Postfix is opening a separate SMTP session with the remote server for each message coming in from the app server, and completing and closing the remote SMTP session before returning to and closing the SMTP session with the local app server.

We would like to see the Postfix server accept mail as fast as possible from the local app server, queue it, then deliver it to the remote SMTP server with high concurrency (by this I mean simultaneous SMTP sessions, is that the right term?), and multiple (~100) messages per SMTP session (what is the correct term for this?). We need to relay 70K unique messages through this system in an hour.

My configs are below.

1. How does Postfix handle relayhost? How can I verify that Postfix is behaving this way, or not?
2. How can I force Postfix to do what we want?

Thank you in advance for any advice!

-- Aaron

Relevant parts of main.cf:
mydestination = $myhostname, localhost.$mydomain, localhost
smtp_sasl_auth_enable = yes
smtp_sasl_password_maps = static:<username>:<password>
smtp_sasl_security_options = noanonymous
smtp_tls_security_level = may
header_size_limit = 4096000
relayhost = [<remote.smtp.server.com>]:12345

Last edited by acutchin; 5th March 2011 at 00:23.
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Old 5th March 2011, 15:16
falko falko is offline
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