Does Outlook keep asking you for the password to connect to the server even when you've selected the "Remember password" check box?
There are many reasons why sending or receiving a message could fail. This guide provides solutions to solve your send/receive errors with Outlook.
Update Rollup 6 for Exchange 2007 Service Pack 3 is now available.
A Rollup Update has been released for Outlook 2016. This is a non-security update which contains 8 documented improvements fixes.
Automatically organize your mailbox by color coding specific Email messages, Calendar items, Contacts and Tasks based on your specified properties.
Security updates have been released for Exchange 2013, Exchange 2016 and Exchange 2019.
Security updates have been released for Exchange 2016 and Exchange 2019. They address 1 vulnerability which is rated "more likely" to be exploited so it is really recommended to update as soon as possible!