[Mimedefang] Timeouts...

Cormack, Ken kcormack at acs.roadway.com
Thu Jun 19 14:12:00 EDT 2003


Over many months running our particular server (with it's workload most
likely being different from yours), we've been running with good success,
with the following timeouts tuned WAY down from the stock settings, and
defined in our sendmail.mc file... (and of course, the resulting .cf file).

With these values, we consistently send and recieve ~2GB of mail daily,
typically totally 80,000 messages a day, with an attachment-size cap of
50MB, on a server sending/receiving data from a 100Mb switched internal
network, and a single T-1 connection to the Internet.

No admin of any sending server has ever complained to us that we are "always
cutting them off" as a result of these timeout settings.  They are
aggressive, yes.  But they also appear to be working fine, for our typical
traffic flow.  Your mileage may vary, of course.

dnl TIMEOUTS (MANY OF THESE)...
define(`confTO_INITIAL', `30s')
define(`confTO_CONNECT', `30s')
define(`confTO_ICONNECT', `30s')
define(`confTO_HELO', `1m')
define(`confTO_MAIL', `2m')
define(`confTO_RCPT', `2m')
define(`confTO_DATAINIT', `2m')
define(`confTO_DATABLOCK', `2m')
define(`confTO_DATAFINAL', `5m')
define(`confTO_RESET', `1m')
define(`confTO_QUIT', `1m')
define(`confTO_MISC', `2m')
define(`confTO_COMMAND', `1m')
define(`confTO_IDENT', `0s')
define(`confTO_FILEOPEN', `1m')
define(`confTO_CONTROL', `1m')
define(`confTO_HOSTSTATUS', `5m')

Ken

-----Original Message-----
From: Lucas Albers [mailto:admin at cs.montana.edu]
Sent: Thursday, June 19, 2003 1:32 PM
To: mimedefang at lists.roaringpenguin.com
Subject: Re: [Mimedefang] Re: Too Many Open Files (again?)


I lowered the timeouts on my system, because of dirty slow evil smtp
servers that would just not close the connection, or resolve ip addresses.
Before I did this I usually had 10-20 open stalled connections at a time.

Has not caused ANY problems on ANY connections since I implemented it 6
months ago.

Sample sendmail entries:

dnl this has never caused problems on mail delivery, it just removes
troublesome
dnl mailers (spammers that won't resolve ip or similar.)
define(`confTO_COMMAND',240s)dnl

dnl timeout on initial outgoing connection
define(`TimoutIconnect=30s')dnl

dnl other items I have configured.
define(`ConnectionRateThrottle',8')dnl limit number of connections per
second that are permitted.
define(`confBAD_RCPT_THROTTLE',`2')dnl limit spammers from trolling for
users on the system, reject all mail after 2 bad recipients.


> * Matlock , Justin <JMatlock at innotrac.com>
>> What ended up happening, is these super-slow connections were opening
>> tons of sockets, but those sockets were never closing.  Sendmail never
>> timed out, because characters were being sent, just *very* slowly.
>
> Sendmail has some very conservative timeout values such as Timeout.rcpt,
> Timeout.datablock, and Timeout.datafinal being set to 1h by default.
> However, I have not experimented with lowering any of them to
> potentially avoid such problems as you are seeing.  With lower timeouts,
> one would expect to see temporary failures and resend attempts rather
> than slow starvation of resources?
>
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