After setup sendmail in my instances running in Digital Ocean cloud, i tried to send few mails using simple php function mail().
And unfortunately, mails sends too slow. About 60 seconds needed to send one email.
i go to logs (/var/log/mail.err), to see whats happens:
Sep 17 11:40:01 ibragimovby sm-msp-queue: My unqualified host name (ibragimovby) unknown; sleeping for retry Sep 17 11:41:01 ibragimovby sm-msp-queue: unable to qualify my own domain name (ibragimovby) -- using short name
So, after i add following line in /etc/hosts:
127.0.0.1 localhost localhost.localdomain ibragimovby
and emails started sending immediately.