You can do it without zapier but you do need to have a script of some kind that is triggered using the webhook and takes the payload and emails it to you. You can’t just program webhooks to send you an email.
For the example you give, you could also enable must approve users but then that would restrict login until you approve the new user manually.
Automation is a good idea! I just tested this and you can actually use an existing automation, if you’re willing to create a user custom field and require your users to complete it at signup.
Though for some potentially universal ones you could have something like:
I accept the terms and conditions
I am not a robot
But a change to the trigger so you could have ‘user created/activated’ for this and not need a superfluous custom field would be
Just a couple of extra notes now I’ve given it an actual run-through
Probably obvious, but for topic_id you can also use a PM topic id (with the added benefit of a shorter email window delay, in case time was of the essence)
One potential downside is that the post is created when a user signs up rather than after they activate their account/verify their email. Though this may not be an important nuance.
You also want to make sure the post creator is the system user (or similar alternative) as you won’t get notified of your own posts if you use yours as the sender.
But just to confirm, a confirmation box custom field works just fine.