How do I eliminate getting 553 error messages

[jwr742]

When I send email messages to some of the people in my address book I get a
System Administrator message as follows: 553 sorry, that domain isn't in
my list of allowed rcpthosts (#5.7.1). The addresses I am sending mail have
my address in their address book. How do I resolve this problem?

 

[VanguardLH]

in

When I send email messages to some of the people in my address book I get a
System Administrator message as follows: 553 sorry, that domain isn't in
my list of allowed rcpthosts (#5.7.1). The addresses I am sending mail have
my address in their address book. How do I resolve this problem?

Configure the e-mail account in Outlook to authenticate to the SMTP mail
host.