Require Mailed Code to Register

Hello,

I am not sure if this is the right place to ask this, but if anyone could help out, that’d be great.

I am starting a site that is heavily based on physical interactions meeting up with people in their area. In order to make sure users are legit, I need to somehow be able to send them a physical postcard with a code on it to complete their registration.

Sounds simple enough but I couldn’t find anything that specifically deals with this. Obviously, this will require a third party service but basically I just need to send a custom code to that service and have them physically mail it to that address so the user can enter that unique code and complete the full registration process.

Any help would be greatly appreciated.