Mail Monitor - Quick reply doesn't work with my ISP

I haven't been able to send a quick reply using my ISP's outgoing mail server. As far as I can tell I've put in exactly what was in my Outlook Expres configuration (which does work) so I'm at a loss to explain why it's not working. I've tried changing the way the outgoing server tab is configured for the account but I always get the following error:

Code:

535 Incorrect authentication data
Incorrect user name and/or password

(aside: I had to type that because you can't copy from the connection log tab)

I have successfully got quick reply to work with my GMail account (although it doesn't always sent the mails out straight away, I have to repeatedly hit check mail box until the mail goes out)