This weekend I spent much time figuring out one annoying issue. In a nutshell, my server has been experiencing strange slowness issues. Some certain .php pages were taking consistently between 1.01 and 1.09 minutes to respond. At some point I found a pattern — it happened only on those pages that had drupal_mail() or php native mail() function.

So I went ahead and tail -f /var/log/mail.err it to find the following:

Jan 25 11:40:01 sms sm-msp-queue[6272]: My unqualified host name (localhost) unknown; sleeping for retry
Jan 25 11:41:01 sms sm-msp-queue[6272]: unable to qualify my own domain name (localhost) -- using short name
Jan 25 11:53:17 sms sendmail[6276]: My unqualified host name (localhost) unknown; sleeping for retry
Jan 25 11:54:17 sms sendmail[6276]: unable to qualify my own domain name (localhost) -- using short name