It's not hard, or expensive. Simply get consent. (Of course, you won't get much personal information on people that way, but that's how it be sometimes.)

Here's an example of how you could do it:

> Hello! I'm setting up a mailing list. If you're interested in receiving occasional updates about what's happening in this part of the community, please put your email address in this form: https://thecommunity.example.eu.org./subscribe

> I'll send you a verification email so nobody else can sign you up. There's also a link there to remove yourself from the list, and you can email [email protected]. any time to remove yourself from the list. (I'll send you a confirmation email to let you know you've been removed from the list.)

> If you want to unsubscribe, please just unsubscribe. If you mark the emails as spam, it might send other people's copies to their spam, too, and it might be months before anybody notices. And if you have any feedback, do let me know.