When installing Microsoft Mail, the Microsoft Mail Server program
checks for a valid Microsoft Mail Data file in the System Folder.
If such a file does not exist, and if you are using a retail version
of the server program, the installation program creates a new
Microsoft Mail Data file and assigns the serial number of the Mail
Server program. You cannot change the serial number of a mail server
once the number has been written to the data file.
If a data file does not exist, and if you are using upgrade version of
the server program, the following message appears:
The Microsoft Mail Server could not be loaded because Update
servers may only be used with an existing "Microsoft Mail Data"
file.
In both cases (if you are using either a retail version or an upgrade
version), if a data file already exists, the Microsoft Mail Server
will update its own internal serial number using the information
contained within the data file.
Because Microsoft Mail uses the serial number contained within the
data file when it communicates with other servers, it is possible to
replace the Microsoft Mail Server file and maintain serial number
integrity.
NOTE: The Microsoft Mail server must be an extension in order to get a
serial number. If the Microsoft Mail Server is running as an
application, it will use the Microsoft Mail Data file's serial
number for operation, but it will not change its internal serial
number to match. This is important if the Microsoft Mail Server is an
upgrade because it will not allow for a new datafile to be created at
a later date.