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:<[email protected]>:
host mx1.mid.com.au [203.12.28.17]: 550 5.7.1 <[email protected]>... server [172.30.30.24] for <[email protected]> rejected address saying "<[email protected]>... User unknown"

 

[stanbusk]

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