GmailClipse is a Gmail Client to manage Gmail accounts. Uses port 80, so if you don't have acces to POP3 and SMTP ports in your office you can find this software very useful. You can use the plugin or the standalone version of GmailClipse. The rich client application version has exactly the same features:

• Advanced search
• Can copy contacts between accounts. Just drag and drop the contacts to the account
• Upload complete or partial projects to Gmail
• New View: Splitted Files
• Can work with multiple emails
• Can read entire conversations