1. People who wouldn't be interested, even after fully learning about the event. Perhaps they don't enjoy the activity, have full schedules, or live too far away.

2. People who would be interested, but don't know about your events. Perhaps they didn't realize there were in-person gatherings for this kind of thing, or didn't know there was one in their city.

3. People who already know about your events in general, but need reminders or notifications about specific instances. Perhaps your event doesn't have a consistent schedule, or someone only wants to attend when they like topic.

You don't want to reach the people in (1): getting your event in front of them just wastes their time and yours. If I went through the phone book and called everyone in my city to tell them about my event, since they're almost all in (1) I'd annoy a lot of people.

You do want to reach the people in (2), but it's hard. Many methods of reaching this group will also reach many people in (1), and so be spammy.

On the other hand, the people in (3) should be really easy to reach: they want your notifications and know they want them. In my social circles, the main tool people used to use was Facebook events: you would join a group, and then you would get notified for every event created in that group.

Unfortunately, in practice this resulted in a lot of event invitations being sent to people in (1). Someone might be only a little bit interested in the group's events. Or they used to be interested, but now they've moved on. Or they never even joined the group, but someone else added them because Facebook experimented with groups working that way for a while. Or it's a huge group mainly used for discussion and then someone creates an event which few people actually want to see. Through a combination of limits, both algorithmic (events may or may not be shown to people based on Facebook's predictions) and strict (you can only invite the subset of a group which you are individually Facebook friends with), this has become much less useful. Then add in the general migration away from Facebook and this is not a good way to reach people in (3).

So what do you do instead? I think announcements mailing lists are a good fit for this group. For example, if you are interested in notifications about events for the contra dance I help organize you could join any of:

• General announcements: bida-announcements
• For musicians: bida-musician-announcements
• For families with young children: bida-family-announcements
• For volunteers: bida-volunteers

Similarly, there's a boston-effective-altruists list where we post announcements for upcoming EA dinners.

We host these lists on Google Groups, and they're self-service. Additionally, we can put out a paper signup form in person, and then enter the email addresses manually afterwards.

I think this works pretty well: people can ask to receive announcements, and if they change their mind they can stop getting them at any point.