Yes, I rebooted the droplet.
A record in the DigitalOcean DNS Manager has the following form: @ 146.185.172.51.
Even now, I tried to send an email, but the email does not reach the addressee. Instead, after 5-6 hours I get a letter from MAILER-DAEMON@control.yourdomain.com (Mail Delivery System) with the title: "Delayed Mail (still being retried) "
and the text:
"Your message could not be delivered for more than 4 hour(s).
It will be retried until it is 5 day(s) old.
For further assistance, please send mail to the postmaster.
If you do so, please include this problem report. You can
delete your own text from the attached returned message.
The mail system
: host mx1.fullspace.ru[81.222.134.105] said: 550
X-Host Lookup Failed: Reverse DNS lookup failed for 146.185.172.51 (failed)
(in reply to RCPT to command)
: host mx1.fullspace.ru[81.222.134.105] said: 550
X-Host Lookup Failed: Reverse DNS lookup failed for 146.185.172.51 (failed)
(in reply to RCPT to command)
Reporting-MTA: dns; control.yourdomain.com
X-Postfix-Queue-ID: 04F76120F00
X-Postfix-Sender: rfc822; dir@yutrust.ru
Arrival-Date: Sat, 16 Nov 2013 17:33:07 +0000 (UTC)
Final-Recipient: rfc822; admin@r*******.ru
Original-Recipient: rfc822;admin@r******.ru
Action: delayed
Status: 4.0.0
Remote-MTA: dns; mx1.fullspace.ru
Diagnostic-Code: smtp; 550 X-Host Lookup Failed: Reverse DNS lookup failed for
146.185.172.51 (failed)
Will-Retry-Until: Thu, 21 Nov 2013 17:33:07 +0000 (UTC) "
What should I do?