Windows Mail server error550 Error number0x800cc79

We have windowd mail and sent a email  with a spelling mistake in the email address.

Now every time we access our email a window pops up saying message could not be sent. the e-mail address was rejected.

error says recipient rejected

invalid domain name

port:25

secure (SSL)

No Service error :550

Error number 0x800ccc 79

Checked with telus our server and they can not get this error window removed

How can we remove this window so it does not pop up every time we access our e-mail account

can someone advie us

Henk