Add option "allow unencrypted only from non-subscribers"
Would be nice to have a configuration option to allow unencrypted mail from non-subscribers only. That is: reject unencrypted mail from members, but accept it from external adresses.
Here's a practical use-case: A group uses schleuder for their internal communication. In order to train their members for send encrypted mails only, they have the list configured to "Receive {authenticated,signed} only". But now, they'd like to use the same list as public contact address (or forward all mail from a public contact address to the schleuder list automatically). For that to work, they'd have to disable the "Receive {authenticated,signed} only" settings, which would be a bad thing.