[imp] Sending Mail

[Michael R. Rogers, II]

My ISP forces me to authenticate at their SMTP relay - when I try to
send a message via IMP, I received the following error:

There was an error sending your message: unable to add recipient
[mrogers at rasses.com]: 553 sorry, that domain isn't in my list of allowed
rcpthosts (#5.7.1)

Are there configuration settings to add a username and password for IMP
to use when connecting to the SMTP server?

Thanks,
Michael