The server is CentOS 5.3 ISPConfig 3. I try to send big email out with slow internet connection. I check log file. It say "timeout = 300". I think the message send take longer than maximum time. Can anyone please tell me where can I change maximum timeout?

If you read http://www.sendmail.org/m4/tweaking_config.html and ^F for "timeout" you'll find all the sendmail.mc configuration options wrt timeouts, their default values and an explanation. However sending overly large files over s slow line is asking for trouble and tweaking your configuration may prove to be no panacea. If possible use compression and attachment chunking.

I'm not using sendmail as smtp. I'm using postfix. Outgoing email always fail to deliver if it is big(about 1.7MB. about 1MB is ok). I can see that outgoing traffic increase after I click send email. That mean email was sending but it seem not complete. I think because it took too long since my slow internet speed. I think it reach maximum sending timeout of postfix. I want to try increasing maximum sending timeout. Please tell me where I can find this option.

Hello Rex,

In a console run:
That will show you all the timeout settings. Then you can reference them against this page: Postfix configuration parameters to find out which to change. Some of them affect other changes as well or have to coincide with other parameters, so read carefully.

I also noticed some message limit parameters in that page, maybe look at them too.

Kind regards,

Eric

There are a lot of timeout option. Which one do you think are the best for above problem?

Hello,

I'm not 'the Postfix expert' but thinking logically and doing some deduction you should be able to find which parameter to change. Since you state that in your log it mentions "timeout = 300", you can change the postconf command as such:
which in my standard Postfix install gives me 16 lines. Check the previously posted link to see what they are. In my opinion I'd try changing this one
since is states in the configuration page:
If that one doesn't work you'll have to play with the other settings, change one at the time, restart postfix, send a mail with a big attachment and see what the result is.

Kind regards,

Eric

How do I modify those setting? I have tried to add them to bottom line of main.cf because I can't find it using search function. I'm not sure if I did it right. I have added qmqpd_timeout, smtpd_timeout, smtp_mail_timeout = 10s, restart postfix and sent email with attachment but the email still reach recipient. So this setting is not correct. Hmm, What should I do?

Hello,

If those settings didn't give you any solution then better set them back to default (remove them from the main.cf) and restart postfix. There are more than three settings so play with the other ones to see if any of them have effect. Again, I'm not the Postfix specialist, but that's the way I would do it, try. On the other hand, do you have this problem with ANY mail with an attachment bigger than 1 Mb or is it recipient specific?

Kind regards,

Eric

Around 1mb email could send out but bigger than 1.7mb will not send out.

Hi,

Is that to any email address you send to? Or just to specific ones. It might be that on the other side the admin has put in some limits on his server.

Kind regards,

Eric

No, I sent to Yahoo.

Hello,

As far as I've found on the internet Yahoo has a limit of 20Mb so that should not be problem. Have you tried changing all the limits one by one yet? Restarting the service after every one and trying to send a mail?

Kind regards,

Eric