A week ago, I found something wrong with my server.
Everything is working, but
1) Some mails were lost. The sender said they sent them out, but we never received.
2) Some mails were late. Like it took a few hours for us to receive them.
3) My php programming page with mail() out function running was slow. Usually it will take less than a second, at that time it took a few seconds.
4) I use mysql dump to back up all database every day. My backup file grows 10K or so every day. But that day, my back up file was 10 K less than the day before, but then the next day, the back up were 20K bigger, so it was back to the normal growth. Something was wrong when that day I backed up 10 K less than the day before. I didn't delete large amount records that day. I roughly check up the backup file, it seems all the databases were backed up.
5) When I found there might be something wrong, I check my qmail queue. There were 2800 mails in the queue, but none processed email was 0 (so it is not too bad). Not good, but not a serious problem, either.
6) I checked the mail queue. Only found 1 small problem, 1 of our php page was attacked by guestbook email spam. But the attack was not seious, up to 200 spam through that page a day. And due to the guestbook was trying to cc to another ISP, these 200 spam a day through our attacked page from our server were rejected by that ISP, sitting in the queue. I fixed it. But even that problem (200 spam attack a day on one php page) was too small to affect the server.
7) I blocked that guestbook email spam attack, and now the mail in the qmail queue is 1400 now.
8) I had some sites still set up as "catch all bounce", I think if I change them to "catch all delete", it will reduce some mail server loads.
Now it seems running fine. But I would like to pinpoint what was wrong? I only found that 200 spam a day attack on one of our site's php guestbook page. I fixed it and the server problem seems solved. My worry is that it seems to me that "200 spam a day attack on one of our site's php guestbook page" should not have a results caused my server mail slow and mysql back up running problem etc. But the fact is that I fixed that spam problem and it seemed to me the server problem was solved.
Any ideas that what I can check for the possible problems?
