Can no send email from Word

[user]

Problem: I can no sent Word document, or Excel doc
directly from this applications use E-mail button. I get
error:
"The message could not be sent because one of the
recipients was rejected by the server. The rejected e-mail
address was '(e-mail address removed)'. Subject 'test',
Account: 'pop.myhost.com', Server: 'mail.myhost.com',
Protocol: SMTP, Server Response: '553 sorry, that domain
isn't in my list of allowed rcpthosts (#5.7.1)', Port: 25,
Secure(SSL): No, Server Error: 553, Error Number:
0x800CCC79"
Outlook work normally. What settings I should configure
and how to send email directly from Word/Excel?

I find also that alert message contains also near
40 "Unsent messages", though I have no any unsent messages
in my "Unsent massages" folder, probably its some old
items, and I dont want they will sent when i solve problem.

 

[Brian Tillman]

"The message could not be sent because one of the
recipients was rejected by the server. The rejected e-mail
address was '(e-mail address removed)'. Subject 'test',
Account: 'pop.myhost.com', Server: 'mail.myhost.com',
Protocol: SMTP, Server Response: '553 sorry, that domain
isn't in my list of allowed rcpthosts (#5.7.1)', Port: 25,
Secure(SSL): No, Server Error: 553, Error Number:
0x800CCC79"

Often caused by not properly authenticating to the outgoing server.