[cp-global] fixed a problem with mailing list configuration

[Kai Engert]

When I recently migrated the cryptoparty.is domain to another DNS
server, I made a mistake.

Instead of configuring the MX hostname to an IP address directly, I
configured it as a CNAME, but I just learned that's forbidden.

I've fixed the DNS, and the fix should become effective within the next
15 minutes.

I'm sorry for this mistake.
If you experienced problems posting to the cryptoparty.is mailing lists,
please try again in 15 minutes.

Kai