Swift_TransportException' with message 'Expected response code 220 but got code "", with message code example

Example: swift_transportexception expected response code 220 but got an empty response

This problem can generally occur when you do not enable two step verification for the gmail account (which can be done here) you are using to send an email. So first, enable two step verification, you can find plenty of resources for enabling two step verification. After you enable it, then you have to create an app password. And use the app password in your .env file. When you are done with it, your .env file will look something like.

MAIL_DRIVER=smtp
MAIL_HOST=smtp.gmail.com
MAIL_PORT=587
MAIL_USERNAME=<<your email address>>
MAIL_PASSWORD=<<app password>>
MAIL_ENCRYPTION=tls
and your mail.php

<?php

return [
    'driver' => env('MAIL_DRIVER', 'smtp'),
    'host' => env('MAIL_HOST', 'smtp.gmail.com'),
    'port' => env('MAIL_PORT', 587),
    'from' => ['address' => '<<your email>>', 'name' => '<<any name>>'],
    'encryption' => env('MAIL_ENCRYPTION', 'tls'),
    'username' => env('MAIL_USERNAME'),
    'password' => env('MAIL_PASSWORD'),
    'sendmail' => '/usr/sbin/sendmail -bs',
    'pretend' => false,

];
After doing so, run php artisan config:cache and php artisan config:clear, then check, email should work.