It takes ~15 seconds to send single e-mail using sendmail.


Jul 31 09:52:42 piotr-probook sendmail[2912]: My unqualified host name (piotr-probook) unknown; sleeping for retry



/etc/hosts:   piotr-probook localdev localhost router


# hosts file (normally /etc/hosts)
O HostsFile=/etc/hosts

Obviously I can ping piotr-probook host and HTTP server popups in browser when i type url http://piotr-probook

What am I doing wrong? How to fix the problem?

  • Your question and Problem is unclear. Please add more information about what you're trying to archive and what your Problems are (e.g. How do you use sendmail? In a PHP script? Python? Java? Is Apache involved?). Basically: What are you doing?
    – mondjunge
    Jul 31, 2013 at 9:20
  • @mondjunge My problem is quite clear. It takes ~15 seconds to send single e-mail using sendmail. I even posted the cause of the issue (see log), and I am just asking how to fix it. I just want to execute sendmail -t mail.txt. No PHP, Java, etc. plain sendmail.
    – Piotr
    Jul 31, 2013 at 9:55
  • 1
    Got the answer: superuser.com/a/626219/242163
    – Piotr
    Jul 31, 2013 at 10:22

2 Answers 2


The above answer didn't work for me. So I am posting here what I have done to make it work.

Installed send mail through terminal

apt-get install sendmail

then opened the hosts file

# edited from: sudo gedit etc/hosts
sudo gedit /etc/hosts

replaced the the line localhost

with localhost localhost.localdomain mydomainname

To get the domain name please type


in terminal and run.

restart apache

sudo service apache2 restart
  • 2
    sendmail should not be related to apache
    – Zitrax
    Jan 30, 2015 at 14:54
  • @Zitrax i didn't get you. Can you please explain what do you mean?
    – Mad Angle
    Apr 2, 2015 at 6:16
  • 1
    Your last step restarts apache, I just meant that shouldn't be needed for fixing the sendmail issue.
    – Zitrax
    Apr 2, 2015 at 7:38
  • The apache restart ins't necessary I'm guessing, since you changed the hosts file and it is independent form apache. Anyway, I might be wrong and restarting apache also does something weird to sendmail, maybe it touches some files used by both Apache and Senmail but I doubt it.
    – loco.loop
    Sep 1, 2016 at 19:13

Got the answer at superuser.com https://superuser.com/a/626219/242163:

Sendmail requires that the result of "hostname" be a fully qualified domain name to start cleanly.

Set the hostname to something like piotr-probook.localdomain and update /etc/hosts.

/etc/hosts   piotr-probook.localdomain piotr-probook localdev localhost
  • Also make sure you have a resolvable FQDN in /etc/mailname
    – jeremiah
    Aug 1, 2013 at 8:08
  • in my case localhost.localdomain along with localhoat and hostname was the missing piece (debian's sendmail inside docker)
    – vladkras
    Jun 19, 2017 at 9:36

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