[System-dt] Updated subscription policy to list

Hi all,

Looks like we got a human or more sophisticated bot spammer, so I've removed veragarth@gmail.commailto:veragarth@gmail.com from the list, banned them, and updated the subscription policy to require moderator acceptance (new) in addition to subscriber confirmation (as before).

If you know anyone trying to legitimately subscribe & having trouble, please let me and Stefano know, as sometimes the moderator confirmation emails get filtered as spam by Microsoft Outlook :(

Thanks & regards, Nathalie