You would not want multiple instances of the programs to be running simultaneously and interferring with each other. Emmesmail uses lockfiles, residing in the TEMP directory and ending in .LCK, to prevent this from happening. Because of our use of lockfiles, there are two instances in which Emmesmail will not open and run; one is entirely normal, and the other, not.
The normal instance when Emmesmail will not simply open and run is for a variable length of time after Emmesmail has just exited with requests for messages to be mailed. Although in this case it appears as if Emmesmail has exited, actually, msv is running in background until msm, also running in background, has finished communicating with your SMTP server about sending all the outgoing email messages. Double-clicking the Emmesmail icon, will not bring msv up and running until the msv running in background finishes. The solution in this case, is to just be patient.
There is one abnormal case when Emmesmail will not run. Sometimes, when a program exits prematurely (crashes!), the lock file or files persist, keeping the application from running again.
If Emmesmail, or one of it's components won't run, the lockfiles need to be removed. You may do this directly if you know how, or, if things have been installed properly and ClearLocks.bat is in the StartUp directory, a simple reboot (Windows restart) will get things behaving properly again.