How to set up Cyrillic display when sending mail in Yii2?

Question

Yii

We have a basic yii2 template.
The config is set to:

'mailer' => [
            'class' => 'yii\swiftmailer\Mailer',
            'useFileTransport' => true,
        ],

Messages arrive in the runtime/mail folder like this:

Message-ID: <[email protected]>
Date: Thu, 23 Feb 2017 10:36:22 +0300
Subject: =?utf-8?Q?=D0=A1=D1=83=D0=B1=D0=B4=D0=B6=D0=B5=D0=BA=D1=82?=
From: =?utf-8?Q?=D0=9D=D0=BE=D1=80=D0=BC=D0=B0=D0=BD?=
 <[email protected]>
To: [email protected]
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable

=D0=A2=D0=B5=D0=BB=D0=BE =D1=81=D0=BE=D0=BE=D0=B1=D1=89=D0=B5=D0=BD=D0=
=B8=D1=8F

How to set the encoding correctly?

Answer 1

Good morning.
Open the file with an email client and you will see the normal content of the letter, with Cyrillic.