Make sure the specified user has full control of the users directory tree in the IMail directory and any mailboxes that will receive mail. Note that if you set the Allow service to interact with desktop option, the SMTP service will run under the current logged on user account. Make sure you send two or three test messages after installation and look in the syslog file and in the event log. If the SMTP service cannot create the lock file, the permissions are probably set incorrectly. If you like this site, tell your friends.
All trademarks used are the property of their respective owners.