OK, this one seems resolved - the issue was in IPv6,
Just set inet_protocols=ipv4 in /etc/postfx/main.cf, restart postfix.
Now emails are forwarded:
postfix/smtp: EFC4D1C11D5: to=, orig_to=, relay=aspmx.l.google.com[18.104.22.168]:25, delay=6.3, delays=0.3/0/5.2/0.73, dsn=2.0.
0, status=sent (250 2.0.0 OK 1384239619 cl1si1153461bkc.228 - gsmtp)
status sent, but not appear come to gmail, but this is another story :)