Dave, there's a lot that can be going on here and it could lead several different directions. Have you confirmed, first of all, that the client machine can see the Zimbra server, and second, that the necessary ports (110 for POP, 25 for SMTP, 993 for secure IMAP, 995 secure POP, 465 secure SMTP) are available?
If you're using the unsecure ports (not recommended), have you enabled clear text login on the GUI? If you aren't, have you enabled SSL/TLS on your client?
Just in case it's a special joy of Outlook, have you tried a different client such as Outlook Express or Thunderbird?
Finally, log onto your Zimbra box at the command line and have a look at /var/log/zimbra.log and see if there are any errors from failed attempts to log in.
Any of these items may help you to debug where the issue is.
Cheers,
Dan |