You should not store the message, because there's no guarantee that it will stay the same. Use instead exit codes:
0 - Files were copied without error.
1 - No files were found to copy.
2 - The user pressed CTRL+C to terminate xcopy.
4 - Initialization error occurred. There is not enough memory or disk space, or you entered an invalid drive name or invalid syntax on the command line.
5 - Disk write error occurred.
thus in case of "File not found", xcode will return exit code '1'. Then you can send your email.
It could be, for example, something like this this could be an example:
set my_errorlevel=0
xcopy....
if ERRORLEVEL 1 (
set my_errorlevel=%errorlevel%
) else echo Success: Polysystems Directory was successfully promoted. 1>>"%logfile%" 2>&1
...
exit /b %my_errorlevel%