Send Mail via SMTP in Yii2 basic

Open the configuration file /config/web.php and add sending mail setting in array element components: 

<?php

$params = require(__DIR__ . '/params.php');

$config = [

     //...

     'components' => [
         'mailer' => [
             'class' => 'yii\swiftmailer\Mailer',
              'viewPath' => '@app/mail',
              'transport' => [
                  'class' => 'Swift_SmtpTransport',
                  'host' => 'smtp.yandex.ru',
                  'username' => '<username>@<yourDomain>',
                  'password' => '<userPassword>',
                  'port' => 465,
                  'encryption' => 'ssl',
              ],
              'useFileTransport' => false,
        ],
    ],
    //...
];

Where <username>@<yourDomain> - e-mail with a letter which will be sent (for example: info@devreadwrite.com), <userpassword> - password from the mailbox <username>@<yourdomain>.

To send mail use the following code in the correct location: 

Yii::$app->mailer->compose()
    ->setFrom('<fromUsername>@<yourDomain>')
    ->setTo('<user@Email>')
    ->setSubject('Уведемление с сайта <yourDomain>') // тема письма
    ->setTextBody('Текстовая версия письма (без HTML)')
    ->setHtmlBody('<p>HTML версия письма</p>')
    ->send();

Where <fromUsername>@<yourDomain> - sender e-mail (<username>@<yourDomain>), <user@Email> - recipient e-mail.

Send Mail via SMTP in Yii2 advanced

Send Mail via SMTP in Yii2 advanced virtually identical as to send in basic. Open the configuration file /common/config/main-local.php and add sending mail setting in array element components: 

<?php
return [
    'components' => [
        //...
        'mailer' => [
             'class' => 'yii\swiftmailer\Mailer',
              'viewPath' => '@common/mail',
              'transport' => [
                  'class' => 'Swift_SmtpTransport',
                  'host' => 'smtp.yandex.ru',
                  'username' => '<username>@<yourDomain>',
                  'password' => '<userPassword>',
                  'port' => 465,
                  'encryption' => 'ssl',
              ],
              'useFileTransport' => false,
        ],
    ],
];

And send in the right place: 

Yii::$app->mailer->compose()
    ->setFrom('<fromUsername>@<yourDomain>')
    ->setTo('<user@Email>')
    ->setSubject('Уведемление с сайта <yourDomain>') // тема письма
    ->setTextBody('Текстовая версия письма (без HTML)')
    ->setHtmlBody('<p>HTML версия письма</p>')
    ->send();

Differences in these examples only the configuration file and value of viewPath. Enjoy using.