Given that Twitter doesn’t provide users’ email addresses to apps [1], how can a Twitter app contact its users?
One thing we’ve done is to have a corresponding Twitter account for our app, and whenever a new user signed up to our app through Twitter, we would follow them. But even so, we can’t DM them from this account unless they follow us back. We can tweet “at” them (via mentions), but public tweets are out of the question for private notifications, and even if that weren’t the case, users aren’t notified of mentions unless they follow us, too.
Is there any other possible way then a Twitter app can contact its users?
[One possibility that would be great would be if apps could DM their users. This would still be independent of whether that app could access their users’ DMs. That would let apps notify users (which is an important requirement for many apps), while still letting Twitter protect its users’ email addresses.]
The answer to this question is pretty simple: you can’t.
Not entirely true, of course. There’s @mentions, DMs and any notification feature your development platform offers, such as push notifications on smartphones. Then there’s e-mails (just offer a newsletter to the user). But Twitter doesn’t offer this to you, and probably won’t.