Where is the registration module in the Invision Power Board?

Question

CMS

The other day there was a problem - on one of the forums under my control, registration stopped working in the regular mode.
That is, a new record is added to the database, but a letter (which contains the account activation key) with confirmation of the email address does not come to the person.
What could be the problem? Maybe the file that sends the letter to the user is glitched? I searched the engine but couldn't find it.

Answer 1

and can you change the type of activity if you can not solve this issue?