I had recieve the error
#< #5.1.3 SMTP; 553 sorry, your domain does not exists.> #SMTP#
What does this means?
It is a message from server with sendmail, send to domain3 (which uses ms exchange).
Full error mail from exchange (sorry, not exact message, but translated from ru to en)
Diagnostic info for administrators: Forming server: domain1_with_sendmail user@domain3 #< #5.1.3 SMTP; 553 sorry, your domain does not exists.> #SMTP#
Does Exchange change text description from remote smtp error?
There is "MX" record for domain3 and no "A" records for domain3, only one for "www.domain3"
Update" all domains are public and have fully-qualified names, all dns's are accessible."
Update2: domain1 has only "A" record, but not the MX one. Can it be a problem?