451 error on hMailServer

[s.r]

Good time of the day. I configured hMailServer with RoundCube web-based interface. But I have problems with sending on some hosts (i.e. mail.ru).
I tried sending messages from Evolution and everything was fine. And sending from RoundCube to "mail.ru"-server was rejected and I got log message "RECEIVED: 451 Try again later". RoundCube haven't got any error message.
This problem I described on hMailServer forum at http://www.hmailserver.com/forum/viewtopic.php?f=7&t=14692&start=0.

P.S. Sorry for my English((

[rosali]

Where is the problem? RoundCube delivers the message to your SMTP server. SMTP server sends the message and gets error response 451, which means that the other side has Greylisting (Greylisting - Wikipedia, the free encyclopedia) enabled. Now your SMTP server should queue the message for resending (f.e. 5 minutes later).

I see nothing where RoundCube is involved.

P.S.: Hmmm, does the baviour you described change, if you set $rcmail_config['smtp_helo_host'] accordingly to smtp server host name?