A request for the devs about mail.

[FaileExperiment]

Isn't that what the FC login message is for?

You could use the FC login message for that, but it isn't ideal and only somewhat serves the purpose, especially if you want to do multiple events with descriptions. What would be more useful is some kind of in-game FC calendar. Though I'd bet SE wouldn't be able to do it due to <server_capacity_issue_here>.

[aerialrave]

What would be more useful is some kind of in-game FC calendar.

This system exists outside of the game in the Lodestone. Unfortunately not many people use it or even know that it exists. Japanese people use it way more than we do, even for such mundane things as recruiting for a single party which we generally use the PF for.