The limit is there because the note is stored in a field in the alarms file.
If every record in the alarms file has a 5000 character field then you can imagine how big the file would become, and how much memory it would take.
There is probably another way to address the problem, but right now I am just filling you in on why there is a restriction.
The short answer is if the note is so huge then it would probably be better to write it into a separate file, and then include the file as an attachment.
The long answer is for me to rethink how to store notes for email alarms.
Yes, in the future I do have plans for html emails from KA