Gerard Paul Java enscribed thusly:
> Hi all,
> Here's something strange with sendmail. I have a long alias file with
> well over thousand e-mail addresses. Upon sending mail though to that
> alias, the addresses to the end of the list do not receive the mail, even
> after several hours. All addresses are on another mail server, so my
> machine has to send the mail over using SMTP.
> Is this already a known problem or is this some kind of limit with
> sendmail? If so can someone give advice? It
> basically results in the same thing if I used a .forward file. Shorter
> lists do not pose a problem.
People who have attempted to run mailing lists with over 1000
subscribers can tell you that this is a familiar phenomenon. The problem
is that sendmail takes a given message and sends it to one recepient at a
time sequentially through the list. Every time you run into an address that
takes a while to resolve or contact or transfer, it holds ALL of the following
messages up. On a mailing list with close to 3000 subscribers, I saw this
latency reach as much as 3 days depending on slow addresses and network
conditions.
You really have two choices (each of which have choices)...
There are some mailing list splitters that will take large lists
of addresses, sort them my host/domain, and split the list into smaller
sublists. They then send a copy of the message to each of the smaller
lists. This means that sendmail has smaller lists to deal with and that
more than one copy of sendmail can be delivering your message at one time.
Unfortunately, it also means that you end up with multiple copies of
sendmail cranking on your system at once and that can use a significant
amount of memory and kernel inodes. It's also highly inconsistant, since
sendmail only starts up one "dequeue process" per queueing cycle. So
sometimes you will have one sendmail taking just as long as before,
sometimes you may have twenty... I tried that route and really was not
happy with it in the long run.
The other choice is to go with one of higher performance MTA's
(Mail Transport Agents) such as QMail or PostFix. QMail can deliver mailing
lists better than two orders of magnitude faster than sendmail. It also
appears to be easier on system resource demand that sendmail, just make sure
you have enough kernel inodes. QMail makes a lot of noise about security,
but I would never use it for security reasons. I've had it brain-fart
several times on system resource exhaustion (ran out of inodes on the spool
file system once and it farted empty messages to all of our subscribers)
and seems to have poor error detection and recovery. Managing it's queue
is fraught with peril (remove the wrong message file and you will get
megabytes of syslog complaints!) so use one of the "contrib" scripts rather
than trusting your ability to remove file and QMail's ability to deal with
inconsistancies in his file system (it has none).
PostFix is another high performance mailer that some say outperforms
QMail. I haven't had a chance to test that yet, but I'm getting ready
to dump all of my QMail installations in favor of PostFix if it proves
to require less "babysitting" than QMail. PostFix is done by Wiese Venema
(I hope I spelled that right) one of the authors of Satan.
QMail has been around a lot longer than PostFix so it has a longer
track record. Unfortunately, the author, Dan Berstien, has a reputation of
being "less than responsive" and having a bit of an attitude. I'm not
sure how Weise compares in that regard, but a minor flame war errupted
between the two up on BugTraq recently which went on until Aleph1 got
fed up and cut the thread off entirely. Dan was flaming Weise over some
initial problems with PostFix while blythly forgetting about the early
problems he had with QMail (including at least one Denial of Service attack
which would crash an entire system).
> ----------------------------------------------------------------
> Gerard Paul R. Java
> System Administrator, Mosaic Communications Cebu
> primary: [EMAIL PROTECTED]
> secondary: [EMAIL PROTECTED]
Mike
--
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NIC whois: MHW9 | An optimist believes we live in the best of all
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