I have a situation with my host smtp settings that is driving me crazy.  When i enter the correct information in the fields and click "test" I get various errors, usually :There has been an error trying to send the test email. The error is:

Mailbox unavailable. The server response was: sorry, no mailbox here by that name (#5.1.1)

If I sent may via the newsletters module it works fine.  I have also used telnet to verify that I can send mail through the mail server from the address in the host module  the only time I get errors is when sending mail to a non-existent e-mail address.

So the questions are: what exactly happens when 'test' is clicked - what e-mail address is the recipient and how can that be changed?  Also How can one trace what is happening during the process?  - I'd like to be able to see the conversation between the application and the mail server. 

Anyone have any insight into this?

the email addresses are valid.  They are the same for both.  to What e-mail address is the test supposed to be sending email?