That’s the documentation you linked earlier; I had a look at that then. The scripts described there are *-by-mail.sh; the mail-*-notification.sh scripts are other scripts and need to be defined accordingly in Director (easiest: as internal commands), or per fixed external definition. You have a lot of leeway on your notification scripts with Icinga.
“One problem after another” is a good description of life as an i.t. admin.*.
Describe your problem in a new thread, documenting how your memory script was set up as command in Director, and how the service template looks that you set up for it, etc., and I promise to have a look at it (you may have to give me a nudge - I pass by here perhaps once a week as a rule).
(* Paul Simon sang on his Graceland album: “The thought that life could be better is written indelibly onto our hearts” - that’s my admin. motto 
)
P.S. (late edit): I see you already opened a thread on the memory problem. I think “log1c” is doing a good job of advising you there… Be careful what you call what, i.e. usual Icinga jargon; a command definition is not a “service object”. In general it’s a good idea in my experience to always have a service template for any command definition, and then import this template in any services you define, either as single services allocated to a host, or as services within a service set.