Lol, I didn't come here to say "Hey, by adding a disabling switch to SendMessage mIRC will be 100% secured".

I don't want to discuss to much about "how a malicious's program can execute mIRC command and other", I already know how that could be done.

I've just noticed that mIRC allows on the one hand disabling "DDE's Server" and on the other hand doesn't allow the same with SendMessage. To let program comunicate with it, mIRC offers those twice possibilities. So the functionnality "disable official program-mIRC's communication" is at 50%. That's the point of my "feature suggestion".

Using a third unofficial method like keystroke (as you've said) is a hacky way and it's not included in the mIRC.chm.

When someone wants to hack a program, he will always choose the easiest security breach. In case of mIRC it will be "SendMessage" or "DDE". If these ones will be disabled, the hacker will need to find another breach (keystroke, editbox, ...) but that will be not easy compared than before (DDE or SendMessage).