What do you mean a new mailbox? Are you setting up as a POP account?
I thought the mail2web server info needed to be on ActiveSync for it to work and work as push e-mail.
Do you get mail2web on your Outlook E-mail inbox or do you have an inbox named mail2web?
Also, this thread goes through how to set it up... it worked for me...
http://ppcgeeks.com/updated-free-dir...,mail2web.html
The invalid recipient error happens to me when trying to send an e-mail via my ISP POP3 account. But mail2web works fine.