Outlook and dial up access

[Dave]

Hello. I use Outlook in the office and have no problems going through my ISP
SMTP server. When I am out of the office on dial up however, I have server
connection issues or SMTP relaying errors. I have tried setting up two
accounts - one that goes through my ISP SMTP and the other through the dial
up (Earthlink) account, using Earthlinks SMTP.

This would work except that since it's trying to send and receive through
both accounts, I still receive errors. How can I setup Outlook to receive
mail from my ISP but send through the dial up without having errors? Is that
possible?

Thanks for any help!

Dave