Super User is a question and answer site for computer enthusiasts and power users. It's 100% free, no registration required.

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

sendmail and qmail both run on the same server. How can I know the one used to send email ?

I have a PHP application that sends email via the mail() function. The SMTP server it uses has both process running. It is a server used for live applications, so I can't stop one process to do some tests.

Thanks Cedric

share|improve this question
I'd make sure that the machine really is as you describe. It's possible to get confused about these things, especially as most Unix/Linux MTSes have a sendmail program image file that is nothing whatsoever to do with the Sendmail software package. There's almost never a need to set up a system in this way with two different MTS softwares running in parallel. (Multiple instances of one package is as exotic a configuration as things normally get.) – JdeBP Jun 18 '11 at 12:45

You will have to look in your php.ini file, under [mail function]. Here, the path to the mail sending binary is specified. Whatever is specified here, the mail() function in PHP will use.

sendmail_path = /usr/sbin/sendmail -t -i

The above one should be the default. So, if you haven't changed anything, PHP will use sendmail.

As @JdeBP mentions, you can also take a quick look at the headers of the mails received. If you look under the various Received sections, you will find some identification of the server software being used.

share|improve this answer
Some systems have sendmail as a symlink to the actual binary provided by the MTA, e.g. sendmail.sendmail or sendmail.qmail. – Ignacio Vazquez-Abrams Jun 17 '11 at 12:25
Oh, okay. Yeah, I'd trace down that one. Like your option though. – slhck Jun 17 '11 at 12:28
+1. The suggestion in the PHP manual is to point sendmail_path directly at qmail_inject, which will be directly indicative with no further research. But in the general case finding out whose binary sendmail_path is pointing to is the right answer for PHP on Unix/Linux. – JdeBP Jun 18 '11 at 12:40
While you're at it, you could mention in your answer that the Received: header fields in the received messages will yield very strong clues as to which software, Sendmail or qmail, processed the mail. Sendmail and qmail write trace information in different forms. – JdeBP Jun 18 '11 at 12:50

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.