If your Internet Mail Service (IMS) does not start, your inbound email will stop flowing.

If you have not run out of free space, a reboot may temporarily resolve the problem. You may notice that the Application Event Log may contain messages from the MSExchangeIMC service:

4070: An error occurred while opening a temporary message file. Verify that                              the message spool directories are configured correctly and are readable by                              the Internet Mail Service.                              4131: An unexpected error occurred in the Internet Mail Service. Information                              about this error is stored in the data portion of this event.
One possible reason for this problem is that the <Drive:>\Exchsrvr\Imcdata\In has been deleted. To fix the problem:

1. Create the <Drive:>\Exchsrvr\Imcdata\In folder.

2. Set Read permissions for Everyone on the folder, so users can't delete it.

3. Restart the IMS service.

If the folder continues to get deleted, enable auditing.