In the file /etc/exim4/exim4.conf.template I found the following line:
domainlist local_domains = MAIN_LOCAL_DOMAINS
You commented out and added:
domainlist local_domains = localhost
After that, the logs written:
2010-09-16 14:24:39 1Ow9ll-00065A-Ce ** firstname.lastname@example.org R=dnslookup T=remote_smtp: SMTP error from remote mail server after MAIL FROM: SIZE=1361: host mx1.example.ru [62.165.37.xx]: 550 , Unknown Sender
What would it mean? As I understand it, this is the PTR server mx1 refuses to accept the letter on the grounds that the letter sent from the user domain example.ru and mail from that domain then steers himself and thinks that he want to cheat? Or is there something else?