SMTP Local > Error 500

Hi,
I’m following the great tutorials from @ben on youtube and everything working fine except that confirmation email is not working.
I tried with sendgrid, mailgun and gmail. Same error : 500.

In the logs, got this :

 server-connect:server Got error? Error: Cannot find module 'nodemailer'
  server-connect:server Require stack:
  server-connect:server - /opt/node_app/lib/modules/mail.js
  server-connect:server - /opt/node_app/lib/core/app.js
  server-connect:server - /opt/node_app/lib/core/middleware.js
  server-connect:server - /opt/node_app/lib/setup/routes.js
  server-connect:server - /opt/node_app/lib/server.js
  server-connect:server - /opt/node_app/index.js
  server-connect:server     at Function.Module._resolveFilename (internal/modules/cjs/loader.js:815:15)
  server-connect:server     at Function.Module._load (internal/modules/cjs/loader.js:667:27)
  server-connect:server     at Module.require (internal/modules/cjs/loader.js:887:19)
  server-connect:server     at require (internal/modules/cjs/helpers.js:74:18)
  server-connect:server     at App.send (/opt/node_app/lib/modules/mail.js:87:28)
  server-connect:server     at App._exec (/opt/node_app/lib/core/app.js:481:57)
  server-connect:server     at App._exec (/opt/node_app/lib/core/app.js:452:28)
  server-connect:server     at processTicksAndRejections (internal/process/task_queues.js:97:5)
  server-connect:server     at async App.exec (/opt/node_app/lib/core/app.js:421:9)
  server-connect:server     at async App.define (/opt/node_app/lib/core/app.js:411:9) {
  server-connect:server   code: 'MODULE_NOT_FOUND',
  server-connect:server   requireStack: [
  server-connect:server     '/opt/node_app/lib/modules/mail.js',
  server-connect:server     '/opt/node_app/lib/core/app.js',
  server-connect:server     '/opt/node_app/lib/core/middleware.js',
  server-connect:server     '/opt/node_app/lib/setup/routes.js',
  server-connect:server     '/opt/node_app/lib/server.js',
  server-connect:server     '/opt/node_app/index.js'
  server-connect:server   ]
  server-connect:server } +6m  

And in the browser :

{
    "status": "500",
    "code": "MODULE_NOT_FOUND",
    "message": "Cannot find module 'nodemailer'\nRequire stack:\n- /opt/node_app/lib/modules/mail.js\n- /opt/node_app/lib/core/app.js\n- /opt/node_app/lib/core/middleware.js\n- /opt/node_app/lib/setup/routes.js\n- /opt/node_app/lib/server.js\n- /opt/node_app/index.js",
    "stack": "Error: Cannot find module 'nodemailer'\nRequire stack:\n- /opt/node_app/lib/modules/mail.js\n- /opt/node_app/lib/core/app.js\n- /opt/node_app/lib/core/middleware.js\n- /opt/node_app/lib/setup/routes.js\n- /opt/node_app/lib/server.js\n- /opt/node_app/index.js\n    at Function.Module._resolveFilename (internal/modules/cjs/loader.js:815:15)\n    at Function.Module._load (internal/modules/cjs/loader.js:667:27)\n    at Module.require (internal/modules/cjs/loader.js:887:19)\n    at require (internal/modules/cjs/helpers.js:74:18)\n    at App.send (/opt/node_app/lib/modules/mail.js:87:28)\n    at App._exec (/opt/node_app/lib/core/app.js:481:57)\n    at App._exec (/opt/node_app/lib/core/app.js:452:28)\n    at processTicksAndRejections (internal/process/task_queues.js:97:5)\n    at async App.exec (/opt/node_app/lib/core/app.js:421:9)\n    at async App.define (/opt/node_app/lib/core/app.js:411:9)"
} 

I have installed nodemailer, but still got the same issue.
There is no way to use API instead of SMTP? How to fix this error 500 problem?

Thanks for your support.