This is going to be a long message, but please stick with me. This problem
is driving me nuts!
In summary, I am having problems with emails getting stuck when fetched
from qmail-pop3d. They are almost always attached MS Word documents. They
aren't necessarily long, I've got 32k messages that do it and 1M messages.
I'm running on kernel 2.0.39, qmail 1.03, daemontools 0.70, ucspi-tcp 0.88
and a slightly modified checkpassword to handle pop accounts in my virtual
domains. This system has been in place since 1999 and has always had an
occasional problem but recently I am getting 1 or 2 messages a week that are
sticking.
I have 2 different cases where this happens. The first is when my home
system, using fetchmail, is downloading messages. If the home machine's
MTU/MRU is set to 1500 or 1480 the messages in question will hang. If I
change the MRU to 576 then they pass through. I don't know if any messages
hang using 576, but I haven't seen any. My MTU/MRU has to be set to 1500 so
that we can get to certain webpages, so leaving it at 576 is not an option.
This is all via a dialup diald/ppp session to my ISP (the same one that the
webserver is colocated at).
The other case is from work. I handle all their email and webhosting. They
are connected to the net via direcPC, a win95 machine running winRoute Pro
and the local lan. The upstream side is a modem connection to the same ISP
where the webserver is located. In this case I cannot change the MTU/MRU and
who knows what direcPC is doing as packets pass through their system. To fix
this case I move the mail to the web directory and download it using
Explorer. When we use Agent 1.8 on the lan to download messages from the
webserver it will exhibit the same 'hanging' that I see with the home
system.
In both cases I can watch the connection with 'snort -v -i eth0 port 110'
and the connection just stops cold partway through the message. I've
upgraded the system's kernel from 2.0.36 to 2.0.29 and updated all the qmail
related software but it is still happening. I'm running the qmail services
using the methods described in 'Life with Qmail'.
I've only found a few references to similar problems when searching and no
solutions. Someone else must have run into this before!
Thanks for any help,
Brian
--
Brian C. Lane - Linux Programmer/Consultant/Writer www.brianlane.com
www.nexuscomputing.com
Liberty & Privacy 'zine Editor www.libertynews.org
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I made wine out of raisins so I wouldn't have to wait for it to age.
-- Stephen Wright
