Mail delivery failed: returning message to sender

[mailrock]

Hi,

Out of 76 messages sent I have 50 returned with this message.

Does this always mean that the user is unknown or could it also mean something else?

Thanks

rock

Mail delivery failed: returning message to sender

SMTP error from remote mail server after RCPT TO:<2wayfm@mid.com.au>:
host mx1.mid.com.au [203.12.28.17]: 550 5.7.1 <2wayfm@mid.com.au>... server [172.30.30.24] for <2wayfm@mid.com.au> rejected address saying "<2wayfm@mid.com.au>... User unknown"

[stanbusk]

It means that there is no such address on that server. 'user is unknown'