I have to bump this as I still got the problem.
This is my mail log:
Oct 15 08:47:07 bosiskarijera postfix/qmgr[18791]: 61383C0EA1: from=<root@bosiskarijera.rs>, size=738, nrcpt=1 (queue active)
Oct 15 08:47:10 bosiskarijera postfix/smtp[20943]: 74A9AC0E77: to=<alexx@bosis.rs>, relay=bosis.rs[195.252.110.143]:25, delay=849, delays=829/0.06/20/0, dsn=4.0.0, status=deferred (host bosis.rs[195.252.110.143] refused to talk to me: 451-The server has reached its limit for processing requests from your host. 451 Please try again later.)
Oct 15 08:47:27 bosiskarijera postfix/smtp[21029]: 3DC70C0E9D: to=<nnix@bosis.rs>, relay=bosis.rs[195.252.110.143]:25, delay=757, delays=737/0.02/20/0, dsn=4.0.0, status=deferred (host bosis.rs[195.252.110.143] refused to talk to me: 451-The server has reached its limit for processing requests from your host. 451 Please try again later.)
Oct 15 08:47:27 bosiskarijera postfix/smtp[21031]: 599E4C0E9B: to=<nnix@bosis.rs>, relay=bosis.rs[195.252.110.143]:25, delay=757, delays=737/0/20/0, dsn=4.0.0, status=deferred (host bosis.rs[195.252.110.143] refused to talk to me: 451-The server has reached its limit for processing requests from your host. 451 Please try again later.)
Oct 15 08:47:27 bosiskarijera postfix/smtp[21044]: 5D7D8C0E9C: to=<alexx@bosis.rs>, relay=bosis.rs[195.252.110.143]:25, delay=865, delays=845/0.03/20/0, dsn=4.0.0, status=deferred (host bosis.rs[195.252.110.143] refused to talk to me: 451-The server has reached its limit for processing requests from your host. 451 Please try again later.)
Oct 15 08:47:27 bosiskarijera postfix/smtp[21054]: 61383C0EA1: to=<nnix@bosis.rs>, relay=bosis.rs[195.252.110.143]:25, delay=356, delays=336/0.03/20/0, dsn=4.0.0, status=deferred (host bosis.rs[195.252.110.143] refused to talk to me: 451-The server has reached its limit for processing requests from your host. 451 Please try again later.)
Oct 15 08:50:47 bosiskarijera postfix/scache[21038]: statistics: start interval Oct 15 08:47:07
Oct 15 08:50:47 bosiskarijera postfix/scache[21038]: statistics: domain lookup hits=0 miss=3 success=0%
Oct 15 08:50:47 bosiskarijera postfix/scache[21038]: statistics: address lookup hits=0 miss=3 success=0%
Oct 15 08:50:55 bosiskarijera clamd[4946]: SelfCheck: Database status OK.
I did change /etc/postfix/main.cf as per suggestion from the post above, but I still have the problem described.
Any suggestions?