Hi,
I assume you are getting this message on a "send & receive" (normal process). You can get a more detailed picture of what's happening if you (run Outlook) and go to Tools>E-mail Accounts>View or Change existing accounts>select the account; click "Change">click "Test Account Settings". You will see when the process fails. Likely problems (in the setup of the account): Outgoing server needs authentication and the box isn't checked or the information is wrong; Outgoing server port is incorrect (typical default is 25). If this account is for an external (an ISP) site, their tech support can tell you what's needed, if you can't figure it out. Is this a new account being setup, or did it work and now something changed? Let me know, we're happy to help.
---Will