Add support for wildcard domains?

[appeasementPolitik]

In my opinion this should be added, as it takes extra effort to set up a wildcard domain (extra DNS records), which I think makes it likelier that someone would also want to use it for their mail server.

If this gets the green light I can open a pull request.

[LukeSmithxyz]

What do you mean here? I mean the script doesn't set any DNS records and I assume that the A/AAAA records are already set on install.

[appeasementPolitik]

Currently the script checks for a $maildomain certificate and uses it if it exists, and if it does not exist it generates a new certificate for $maildomain. I am proposing that it also checks specifically for a \*\.$domain wildcard certificate and uses it if it exists as it is also a valid certificate for $maildomain.

Not to be confused with *.$domain, which is different in regex.

[LukeSmithxyz]

Ah, I see. Good call. I've added that.