I have removed a mailbox in the connector, after restarting Exchange System Manager I still see it in the list.

The connector configuration is stored in AD. This situation arises when you do not have rights to remove objects from AD. You can check rights by means of the ADSI Edit tool from Windows Server Support Tools.

You can also remove these mailboxes using ADSI edit.

• Press button Start, ' Run... ' also start ' mmc ';
• ' File '-> ' Add/Remove Snap in '-> ' Add... ' add ' ADSI Edit '.
• Press ' Close ', press Ok;
• Right-click on ADSI Edit and choose Connect to
• Under Select a well known Naming Context: choose ' Configuration '.
• Press ' Ok ';
• Open Configuration-> Services-> Microsoft Exchange-> < Name of your organisation>-> Administrative Groups-> First Administrative Group-> Routing Groups-> First Routing Group-> Native POP3 Connector
• There you will see the objects CN=1, CN=2 etc. These are NPC mailboxes. Open their properties. The name of the mailbox is specified in the adminDisplayName attribute.
• Find the mailboxes which need to be removed and remove these CN =...