Hasn't helped so far. Suggestions in the article:

You are not connected to the Internet or a network, or your mail server is
temporarily unavailable.
Definitely connected.
Your account settings are incorrect.
Definitely correct, rechecked so many times it's not funny (plus I set up
Windows Mail already with the same settings, so I know they are correct).
Your user profile in Outlook is damaged.
Perhaps - so I added a new profile - didn't help.
An e-mail item on your POP3 server is damaged.
Don't think so - this should affect Windows Mail too.
The configuration of your AV software is incorrect.
Don't have any installed.
Outlook Express was removed from the computer or the installation is damaged.
Vista doesn't have Outlook Express (has Windows Mail which is working
perfectly).
The configuration of your personal firewall software is incorrect.
Windows Firewall has an exception set for Outlook - no other firewall
installed.

Under advanced options:

Method 1: Start Outlook in safe mode.
Didn't make a difference.
Method 2: Create a new e-mail profile.
As above, no difference.
Method 3: Delete suspicious messages from your mailbox.
No suspicious emails.
Method 4: Check your antivirus vendor’s Web site for additional suggestions.
No antivirus installed.
Method 5: Remove, and then reinstall Outlook Express.
Don't have outlook express (Vista).
Method 6: Verify that all SMTP e-mail addresses in a distribution list are
valid
Settings exactly same as Windows Mail.
Method 7: Examine the configuration of your firewall software.
Windows firewall has Outlook excepted.

Another co-worker who bought a new laptop with Vista and installed Outlook
2007 had the same problem - was able to set up his work email on Windows
Mail, but not on Outlook (Same error message). Not sure what to do next.

"DL" wrote:

http://support.microsoft.com/kb/813514
maybe helps