Nodemailer

Nodemailer - is a package that connects sender mailbox for sending messages (so messages will be saved in Sent folder of the mailbox).

npm init -y
Add script "start:dev": "nodemon app"
npm i nodemailer dotenv
npm i nodemon -D
Create in root of the proj .prettierrc.json
Add .env file in root of project with necessary
- EMAIL_SENDER=... - mailbox from what messages send;
- EMAIL_EXTAPP_PASS=... - some post services use additional password for external applications.
  f.e. EMAIL_EXTAPP_PASS is took
  - "gmail" - in Security/How you sign in to Google/2-Step Verification/App passwords
  
  - "ukr.net" - in Management of IMAP access/Access for external applications
  
  So configs in node.js will be different, f.e. gmail, ukr.net etc.
Before pushing the initial repository to the github remember about adding .gitignore to the project including in the beginning .env

Example 1 - synchro fn send to a one receiver

app.js

Create repo according to MERN - quick guide till moment of user REGISTRATION and LOGIN.
npm i nodemailer
Look up of adding to .env EMAIL_SENDER, EMAIL_EXTAPP_PASS
Create utils\sendMailByNodemailer.js
See the Pen 126__nodemailer__Ex3 by Andrii (@imitator) on CodePen.
P.S. Remember about reexport in utils\index.js
Send email from f.e. controllers\auth\registerCTRL.js

Create repo according to MERN - quick guide till moment of user REGISTRATION and LOGIN.
npm i nodemailer nanoid@3
Look up of adding to .env EMAIL_SENDER, EMAIL_EXTAPP_PASS
Add two fields to models\schemas\user.schema.js
In controllers\auth\registerCTRL.js create verifyCode, add to user object and send email with a code link
In routes\auth.routes.js create verify route
router.get('/verify/:verifyCode', ctrl.verifyCodeCTRL);
controllers\auth\verifyCodeCTRL.js
P.S. Remember about service.findUser, service.updateUserSRV