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I was the operations manager for Smartgroups.com an egroups (yahoogroups) clone. We used two small Sun E250s to send upwards of a million emails a day using qm

I was the operations manager for Smartgroups.com an egroups (yahoogroups) clone. We used two small Sun E250s to send upwards of a million emails a day using qmail and a tweaked version of the Solaris TCP settings to close connections as quickly as possible. These two servers also handled the bounces as well as the usual spam attempts. If I was doing something similar again I'd still used the Solaris/qmail combo as it was very reliable. Our biggest problem was with people marking us as spammers even though they had to sign up to groups to use the service but that's a constant headache in this game. We also had some shell scripts that culled SMTP connections (either incoming or outgoing) that had been help open too long as that helped us deal with DOS attacks. The site also throttled SMTP traffic to give HTTP traffic priority if required as that's OK for SMTP with its store-n-forward architecture but not for HTTP

terra_t 16y ago
I'd second that. Things may have changed recently, but historically, Linux hasn't been a great platform for mail servers because of the file system semantics. (Linux systems can get very ~weird~ under heavy email loads, kinda the way that Windows systems get ~weird~ in everyday desktop operations.) Solaris is very good, and the x-BSDs often do better if you're a free software fanatic.
- mhansen 16y ago
  I don't understand. Can you elaborate on what you mean by 'weird' and why the BSD's do better?
  - terra_t 16y ago
    It has to do with the way fsync works and metadata updates on directories. Linux does a lot more work updating directories, which hurts performance on mail servers in general but really hurts with qmail. Practically you might find your CPU utilization is 2%, but the load average is 50 and you do 'ls' on a directory that has 20 files in in it and it takes 30 seconds.
    - njharman 16y ago
      Huh, thanks! Now I finally know why the hell that happened.

terra_t 16y ago

I'd second that. Things may have changed recently, but historically, Linux hasn't been a great platform for mail servers because of the file system semantics. (Linux systems can get very ~weird~ under heavy email loads, kinda the way that Windows systems get ~weird~ in everyday desktop operations.) Solaris is very good, and the x-BSDs often do better if you're a free software fanatic.

mhansen 16y ago
I don't understand. Can you elaborate on what you mean by 'weird' and why the BSD's do better?
- terra_t 16y ago
  It has to do with the way fsync works and metadata updates on directories. Linux does a lot more work updating directories, which hurts performance on mail servers in general but really hurts with qmail. Practically you might find your CPU utilization is 2%, but the load average is 50 and you do 'ls' on a directory that has 20 files in in it and it takes 30 seconds.
  - njharman 16y ago
    Huh, thanks! Now I finally know why the hell that happened.