在使用swift_mailer时出现了以下错误:

Expected response code 220 but got code "", with message """

解决办法：

这个一般是由于encyption配置导致的

Secure Sockets Layer (SSL)

Transport Layer Security (TLS)

'mailer' => [
    'class' => 'yii\swiftmailer\Mailer',
    'viewPath' => '@common/mail',
    // 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' => 'smtp.163.com',
        'username' => 'jiaowomrwei@163.com',
        'password' => 'xxxxxxxxx',
        'port' => '25',
        'encryption' => 'tls',
    ],
],

再看看163的SMTP配置说明

所以如果使用ssl端口则encyption配置项必须为465/994如果使用非ssl则应该使用25