Exchnange server 5.5 outbound message problem

I have Exchange server 5.5 SP4 installed
Recently i've received a very strange behavior of server.
When sending message with attachments throuth internet mail connector to
some domains message hangs in outbound quee.
In event log appear a new record:
Event ID: 3010
Source: MSExcnahgeIMC
Type: Warning
Category: SMTP Interface Events
Event Description: an attempt to connect to host #host name# failed.


When sending message to the same domain without attachments there is any
problem.

Please help me to resolve that problem.


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