Error 421
1. Access and run the Microsoft Exchange Server Administrator utility. The process used to set up the server will cause the access path to the utility to vary.
2. Locate the 'Connections' icon in the Microsoft Exchange Server Administrator’s left navigation pane. This is for the server that you want to administer. Find the 'Internet Mail Service' icon in the right navigation pane and double click it to open the 'Properties' dialog box.

3. Click the 'Connections' tab, then click the 'Advanced' button. The configuration dialog will open up.
4. Move the number in the 'Max No. of Inbound Connections' higher, until the error is rectified. For example, begin with 100 and if this does not solve the error, continue to go higher until the error is fixed.
5. Close the program dialog boxes to save recent changes.
Error 0X800ccc90/Error 0x800ccc18
6. Open and run Outlook Express and click on the 'Tools' option in the main menu.
7. Choose the 'Accounts' option under the 'Tools' menu.
8. Click on your email account to select it and choose the 'Log on using' option.
9. Click on 'Servers' in the 'Log on using' menu. Select the 'Clear Text' option to rectify this error. You can now log on without any issues.