- Shing-Gene Yung <[EMAIL PROTECTED]>:
| Due to massive network failure on our campus backbone, our dept's
| mail system got quite _messy_. One of the problems we had was having
| the mail server flooded with messages trying to get in but were
| failing because of the intermittent network.
|
| We have 2 qmail servers (on 2 different subnets), each being a
| backup for the other (one is a DU4.0d system and the other a
| FreeBSD). The DU system started spawning a lot of qmail-smtpd and
| qmail-queue processes, until the point where the process table was
| max-ed out and this almost brought the system down. Fortunately I
| managed to kill off the smtpd/queue processes and turn off mail
| reception until the network was up again. I suppose, in retrospect,
| I should have ulimited the qmail daemons? Or was there something
| else I could have done?
Use the -c option to tcpserver to limit the number of incoming
connections.
| The FreeBSD system turned out to be o.k. (I couldn't telnet in to
| turn off the mail, or check on it at all) since it queued up the
| messages meant for the other server, and when the server came back
| online, they were sent back there. Any ideas as to why the FreeBSD
| server survived over the DU box?
I would expect FreeBSD to have no problems with tcpserver's default of
max 40 connections (which translates to 80 processes). But then, I
never even heard of DU, so I really shouldn't speculate.
| Poking around the queue dirs on the DU box, I saw that 99% of the
| queued messages were zero length, while a handfull had complete
| messages and others only partial content. I deleted the the entire
| queue (since it was useless anyway after saving the complete
| messages), or rather, deleted the entire /var/qmail and
| re-installed. Question is, did I actually lose any mail??
Only inspecting the log can answer that question, I think.
| What does qmail do when it is unable to complete sending a message
| to another qmail server?
The message remains in the queue and are retried for up to a week.
(This is guaranteed, as long as the file system is intact and no ones
messes with the queue.)
| I noticed that some of my personal mail had duplicate copies...are
| these the ones from the deleted queue?
Maybe. The usual reason for duplicates is when the connection is lost
after the SMTP server has OK'd receipt of the message, but before the
client has seen that response. I bet that could happen quite a bit,
when you have severe network problems!
- Harald
