Undeliverable email

[Vince]

I send and receive email many times a day, but there are
two email addresses (both are family members) where I get
a message from the System Administrator saying:

Your message did not reach some or all of the intended
recipients.

Subject: test
Sent: Date/Time

The following recipients could not be reached:

(person's name and email address, Date/Time
553 sorry, that domain isn't in my list of allowed
rcpthosts(#5.7.1)

Can anybody help me with solving this problem?

Thanks

 

[Jeff Stephenson [MSFT]]

You probably need to set up authentication to your outgoing mail server,
which can be done on the "Outgoing Server" tab for your mail account.