Reply to Craigslist from non-default account in Outlook 2007

[Octopus]

I have 3 accounts set up in my Outlook 2007. It defaults to my personal account. When I browse craigslist and I want to respond to an ad, I don't send from my personal account until I can verfify that the party on the other end isn't some sort of scammer, so I change the account to send the reply from. But when I do that, the email stays in my outbox. It never goes anywhere. Also, I get an error message saying "The operation cannot be performed because the server is offline." 0x80040126 If I don't change from the default account, it sends fine.