Many websites take the following steps: 1: Request to enter your email address on the new registration screen ↓ 2: Send an email with a link for official registration to that email address ↓ 3: Fill in the required items on the form that has transitioned from the link ↓ 4: Registration completed
If user registration is completed without receiving an email, you can create an infinite number of accounts. In that case, there is a possibility that it will be used illegally, so the aim is to complicate the procedure and prevent unauthorized use.
To establish a means of contact with users. If the entered e-mail address is incorrect, it will not be possible to establish contact with the user and even tell that "user registration has been completed". Therefore, we are checking whether the e-mail address can be received normally.
It seems to be implemented using a gem called devise to perform login authentication with Rails.
[* Rails *] How to use devise (rails5 version)
[Reference blog](https://www.ryotaku.com/entry/2019/06/14/%E3%83%A6%E3%83%BC%E3%82%B6%E3%83%BC% E3% 81% AB% E4% BB% AE% E7% 99% BB% E9% 8C% B2% E3% 82% 92% E8% A1% 8C% E3% 82% 8F% E3% 81% 9B% E3% 82% 8B% E7% 90% 86% E7% 94% B1 # Web% E3% 82% B5% E3% 82% A4% E3% 83% 88% E3% 81% A7% E3% 81% AE% E4% BC% 9A% E5% 93% A1% E7% 99% BB% E9% 8C% B2% E3% 81% AE% E6% 89% 8B% E9% A0% 86)