Yii2 smtp error 500 5.5.1 command unrecognized - php

Question

In my Yii2 application i've a contact form that sends email with swift.
I've configured my application in this way:
those are the configurations in web.php:
'mailer' => [
'class' => 'yii\swiftmailer\Mailer',
// send all mails to a file by default. You have to set
// 'useFileTransport' to false and configure a transport
// for the mailer to send real emails
'useFileTransport' => false,
'transport' => [
'class' => 'Swift_SmtpTransport',
'host' => 'authsmtp.myhost.com',
'username' => 'username',
'password' => '************',
'port' => '25',
'encryption' => 'tls',
],
],
and this is the part of my controller where i send the mail:
if($contact->load($post) && $contact->validate())
{
Yii::$app->mailer->compose('request',['contact' => $contact ])
->setFrom('mail1#mail.it')
->setTo('mail2#mail.it')
->setSubject('This is a test email')
->send();
return $this->redirect(['login/index']);
}
I receive a Swift_TransportException with this error:
Expected response code 220 but got code "500", with message "500 5.5.1 command unrecognized"
Is there a way to retrieve more information about the error generated by swift?
This message is too general.
Thanks in advance for all the help

Answer 1

For logging use yii\swiftmailer\Logger:
Logger is a SwiftMailer plugin, which allows passing of the SwiftMailer internal logs to the Yii logging mechanism. Each native SwiftMailer log message will be converted into Yii 'info' log entry.
SMTP ports are 465 or 587 with SSL/TLS, and 25 without. From the Wikipedia page on SMTP:
SMTP by default uses TCP port 25. The protocol for mail submission is the same, but uses port 587. SMTP connections secured by SSL, known as SMTPS, default to port 465 (nonstandard, but sometimes used for legacy reasons).
Unless your server has been explicitly set to use port 25 with SSL/TLS you shouldn't use encryption.