How do I set Calendar alerts default to email instead of messages?

I do custom email alerts to manage my life in iCal. The email stays on my desktop until I delete it whereas I find messages disappear on their own.

I set up all appointments, BDs anniversraries, due dates etc. with email alerts.

It seems every time Apple does an update these alerts default back to messages and I miss critical stuff.

How can I set the alert default

to email and not message?

[Re-Titled by Moderator]