1 Topic by answerman

  • answerman
  • Member
  • Offline
  • Registered: 2011-01-07
  • Posts: 69

Topic: Random SMTP Timeouts

==== Required information ====
- iRedMail version: 0.8.0
- Store mail accounts in which backend (LDAP/MySQL/PGSQL): MySQL
- Linux/BSD distribution name and version: CentOS 5.6
- Related log if you're reporting an issue:
====

Wondering if I need to tweak iRedMail settings as our server gets busier.  We've been getting random SMTP timeout errors over the past few months, and they seem to be getting more frequent.  An example of what happens is that I will compose a message in Thunderbird, attempt to send it, and it will hang on the "connecting to mail.mydomain.com" for a minute or two, and then show a message that the connection to the SMTP server has timed out.  Then, I attempt to send again and it goes immediately.   This seems to be serverwide regardless of the email client used.  I'm wondering if, as we've grown and added accounts (there are about 1000 accounts on this server), if we are exceeding a maximum number of connections and that's why it's timing out.  Could that be the case, and where would I go about increasing the number of connections available?

----

Spider Email Archiver: On-Premises, lightweight email archiving software developed by iRedMail team. Supports Amazon S3 compatible storage and custom branding.

2 Reply by ZhangHuangbin

  • ZhangHuangbin
  • ZhangHuangbin
  • iRedMail Developers
  • Offline
  • Registered: 2009-05-06
  • Posts: 31,094

Re: Random SMTP Timeouts

Did you find any related error in Postfix log file on iRedMail server?

You may want to increase value for Postfix parameter "default_process_limit":
http://www.postfix.org/postconf.5.html# … cess_limit

3 Reply by answerman

  • answerman
  • Member
  • Offline
  • Registered: 2011-01-07
  • Posts: 69

Re: Random SMTP Timeouts

No errors in the logs.  I don't see any entry for default_process_limit in main.cf.  I do see it in master.cf but it has no value, just a dash:
*********************************************************
smtp      inet  n       -       -       -       -       smtpd
*********************************************************

Shouldn't it be like this with an entry for maxproc?
*********************************************************
smtp      inet  n       -       -       -       100       smtpd
*********************************************************

I'm pretty sure I have never edited these settings, so I assume they are still from the stock install.

4 Reply by ZhangHuangbin

  • ZhangHuangbin
  • ZhangHuangbin
  • iRedMail Developers
  • Offline
  • Registered: 2009-05-06
  • Posts: 31,094

Re: Random SMTP Timeouts

*) is it possible that your IP address was blocked in iptables due to too many password failures?
*) You can add 'default_process_limit = 100' in Postfix main.cf if this parameter doesn't exist. Change the value to the one you want.

5 Reply by answerman

  • answerman
  • Member
  • Offline
  • Registered: 2011-01-07
  • Posts: 69

Re: Random SMTP Timeouts

ZhangHuangbin wrote:

*) is it possible that your IP address was blocked in iptables due to too many password failures?
*) You can add 'default_process_limit = 100' in Postfix main.cf if this parameter doesn't exist. Change the value to the one you want.

No, it's not a password failure.  Trying to send again after getting the error generally results in the message going through.  I have added 'default_process_limit = 200' to main.cf and restarted Postfix... we'll see if that helps.