Re: Mail delays--temporarily solved

On Apr 23, 2008, at 3:35 PM, Mike Matthews wrote:

All:

As a follow up to a recent post...

In the last week or so, our Tiger (v10.4.11) mail server has really slowed down delivery of its mail. I tried putting in more RAM (now at 1.5 GB) to no avail on our G4 867 PowerMac.

We have about 20 IMAP users and 10 POP users.

It appears that mail is not being processed fast enough by the built-in virus and spam checkers. And Activity Monitor tells me that the CPU is constantly at 100% usage. Thus, mail stacks up in the queue (up to as many as 300 messages to be delivered) with two-hour delivery delays while 30 users pound on the mail server for new mail.

...We had been seeing CPU use maxed out constantly, with two processes for clamAV each accounting for 40+% of the CPU usage. I tried stopping virus and junk scanning earlier, but that seemed to stop the mail queue entirely (perhaps I failed to restart or something).

So, as a short-term fix, we turned off virus scanning and spam filtering on the mail server last weekend (correctly, it appears). Doing so seems to have returned the delivery of messages to their earlier level of speed.

I'm not sure what triggered the sudden delivery delay a couple of weeks ago. But the server was spending inordinate amounts of time filtering and scanning mail rather than delivering it.

Medium-term, we'll either do an upgrade to Leopard or update 10.4.11 to have newer versions of clamAV and clamd, which I believe may solve the problem.

10.4 server by default uses clamscan instead of clamd, which is quite a bit slower. This was due to some past licensing issues/kerfuffle - ie: Apple had no choice but to go with clamscan.

As far as I know that is no longer true.

So certainly one advantage of updating clamav will be more efficient scanning.

A known-good method (tutorial) is here:

(please feel free to make a contribution. I have no affiliation with the site)

Frankly, you're *far* far better off using Postfix's capabilities to reject spam up front rather than burdening your server with processing most or all of it via spamassassin &clamav.

As I always recommend, read up at postfix.org , get the Book of Postfix - http://www.postfix-book.com

and as well, there is a safely pre-chewed tutorial at the topicdesk.com site ("Frontline defense") - safe to use but backup first of course. Far better to understand what that tutorial is accomplishing

and how/why. Plenty of good reading at tthe postfix site, http://www.postfix.org/docs.html  - see the UCE/Virus section and note that none of them are OS X specific: you don't need to install anything with regards to SASL, PAM or postfix itself, and a few other minor adjustments would be needed to use those tutorials as-is. But it can be done easily (done so personally).