[Mailman-Users] Mailman causing strange slowdown in SMTP

Brad Knowles brad at stop.mail-abuse.org
Sat Aug 12 02:33:26 CEST 2006

At 12:42 AM -0500 2006-08-11, Craig Pettersen wrote:

>  Thanks for the response.  The slow down has continued and nothing I've tried
>  has helped.  I answer the questions put to me in context below.  Any further
>  ideas would be greatly appreciated.

Just a guess, but have you stopped the MTA, moved the mail queue 
directory structure aside, re-created the mail queue directory 
structure with the same ownership and permissions, and then restarted 
the MTA?  You'll need to find a way to get all that old mail 
processed, but that would at least get you accepting new mail again 
faster -- until the next time when you have to do this kind of 
process all over again.

The problem here is that mail queue directories get bigger and 
bigger, and never shrink.  So, even if you think you only have a 
hundred files in the queue, if you look in the deep filesystem 
structure there may be space for hundreds of thousands or millions of 
files, dating back from a time when you had a serious backlog in the 
past.  Problem is, when the MTA is trying to create new files in the 
queue directory to represent a given message, the code to create a 
new file has to lock the entire directory structure from all changes 
by any other process, search the entire directory structure to ensure 
that there are no other files by that same name, and only then can it 
actually create the file, unlock the directory, and return the file 
handle to the calling program.

Mailman can suffer from this same problem, too.  Same solution -- 
stop the program, move the queue directory structure aside, recreate 
the queue directory structure with the same ownership and 
permissions, then restart the program.  And you also have to find a 
way to deal with all those old messages sitting in the queue that has 
now been set aside.

The only other thing I can think of is that your MTA is trying to do 
an IDENT query (which usually time out at ten to fifteen seconds), or 
some other sort of anti-spam/anti-virus processing on your outbound 
mail.  If the latter is the case, then you want to turn that off for 
outbound mail from the mailing list, since that should have been 
scanned on input.

Other than that, I'm out of ideas for the moment.

Brad Knowles, <brad at stop.mail-abuse.org>

"Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety."

     -- Benjamin Franklin (1706-1790), reply of the Pennsylvania
     Assembly to the Governor, November 11, 1755

  Founding Individual Sponsor of LOPSA.  See <http://www.lopsa.org/>.

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