maillscanner/postfix saturates bandwidth :-(

Kevin Miller Kevin_Miller at
Mon Sep 24 22:11:18 IST 2012

Check the exchange server, and if there are any pending outbound monster sized messages in the queue still delete them.  Be sure to notify your users, of course.  Next delete them off the outbound postfix server so you can process normal mail uninpeeded.  Then, as others have suggested, put the 3.5 mb file on a web server or use something like dropbox (or better yet, build yourself a zendto server) and have your user(s) just send a link to the URL instead of sending the mail out  to 2000 folks.

Kevin Miller
Network/email Administrator, CBJ MIS Dept.
155 South Seward Street
Juneau, Alaska 99801
Phone: (907) 586-0242, Fax: (907) 586-4500
Registered Linux User No: 307357

-----Original Message-----
From: mailscanner-bounces at [mailto:mailscanner-bounces at] On Behalf Of Harondel J. Sibble
Sent: Monday, September 24, 2012 9:15 AM
To: mailscanner at
Subject: maillscanner/postfix saturates bandwidth :-(

Had an odd situation that started Friday night at one of my clients running a mailscanner/mailwatch mail relay for their internal Exchange 2007 server.

Basically the dsl connection they share with another office was saturated when the office admin did a mailout on friday to about 2000 of their subscribers, each email was about 3.5mb total with conversion overhead.  When I say saturated, I mean in both the upstream and downstream directions.  
According the admin who runs the multitenant network in this office, he was seeing a sustained 1.6mb/s INBOUND connection to my client's firewall while this was happening.

I intially though that someone had hacked in and was injecting spam, but after upstream throttling of the connection and disabling all smtp traffic, I was able to review the messages in the postfix deferred queue and determine they were part of the mailout.

At this point mailq was showing 14 messages with approx 100 recipients total, I could then re-enable smtp traffic (in/out) at the firewall level and emails would be fine sending and receiving, but if I did a postqueue -f, the connection would saturate again until I blocked the smtp traffic, then waited a couple minutes before re-enabling it and the messages went back to being deferred.

I'm trying to figure out the best way to deal witih this moving forward, is there additional throttling I need to do at the postifx level or the mailscanner level or something else.  I was also surprised as my understand of postfix is that it does connection throttling by default.
Harondel J. Sibble
Sibble Computer Consulting
Creating Solutions for the small and medium business computer user.
help at (use pgp keyid 0x3AD5C11D)
(604) 739-3709 (voice)

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