Feature request: [Mailing lists] Export function to export mailing lists into a format that can be copied into mail clients

[Wachizungu]

Is your feature request related to a problem? Please describe.

Yes. I have to combine e-mail addresses from active users on several MISP instances + some other sources, to send out certain communication. This is a rather painful experience. I'm looking for a place where I can maintain these types of lists easily.

In essence, thought is to have a way to automatically generate lists from data in Cerebrate (+ MISPs?), later on potentially with some filtering options (tags perhaps).

Describe the solution you'd like

Extension of the current mailing list system, with an option to export the e-mail list as comma or semicolon separated. Some quick search that comma separated is most common format, but outlook uses semicolons.

Additional context

Probably one of the use cases I'm most looking forward to is having an easy way to create the full mailing lists.