Character Encoding in Plain Text Emails Fails since 2.2.8/2.3.0 due to emails no longer being sent as MIME

[gwharton]

Preconditions (*)

1. Magento 2.2.8 or 2.3+

Steps to reproduce (*)

1. Install vanilla magento
2. Setup valid store email address
3. Create a new email template. Name : "Newsletter Success", Subject : "Newsletter subscription success", Template Content : "You have been successfully subscribed to our newsletter. ö£€"
4. Convert email template to Plain Text and Save
5. Config -> Customer -> Newsletters -> Success Email Template -> "Newsletter Success"
6. Clear cache
7. Go to home page and subscribe to newsletter

Expected result (*)

1. Emails received are MIME emails.
2. All the essential MIME headers such as Content-Type, Content-Transfer-Encoding are preserved.
3. Special Characters are encoded correctly.

Actual result (*)

1. Emails received are not MIME emails.
2. All the essential MIME headers such as Content-Type, Content-Transfer-Encoding are missing.
3. Special characters may not be encoded properly.

This is new behaviour introduced in 2.2.8. See below for comparison of 2.2.7 2.2.8 and 2.3-develop

2.2.7

Email client shows plain text email You have been successfully subscribed to our newsletter. ö£€

Received Email source (some headers clipped)

To: test@domain.com
Subject: Newsletter subscription success
From: Owner <test@domain.com>
Content-Type: text/plain; charset=utf-8
Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
MIME-Version: 1.0
Message-Id: <20190408200546.29448C1894@domain.com>
Date: Mon,  8 Apr 2019 21:05:46 +0100 (BST)

You have been successfully subscribed to our newsletter. =C3=B6=C2=A3=E2=
=82=AC

2.2.8

Email client shows plain text email You have been successfully subscribed to our newsletter. ö£€

Received Email source (some headers clipped)

To: test@domain.com
Subject: Newsletter subscription success
Date: Mon, 08 Apr 2019 20:33:03 +0000
From: test@domain.com
Message-Id: <20190408203304.889F5C16FB@domain.com>

You have been successfully subscribed to our newsletter. ö£€

2.3-develop

Email client shows plain text email You have been successfully subscribed to our newsletter. ö£€

Received Email source (some headers clipped)

To: test@domain.com
Subject: =?utf-8?Q?Newsletter=20subscription=20success?=
Date: Mon, 08 Apr 2019 20:34:39 +0000
From: =?utf-8?Q?Owner?= <test@domain.com>
Message-Id: <20190408203439.7FD9AC16FB@domain.com>

You have been successfully subscribed to our newsletter. ö£€

[m2-assistant]

Hi @gwharton. Thank you for your report.
To help us process this issue please make sure that you provided the following information:

• Summary of the issue
• Information on your environment
• Steps to reproduce
• Expected and actual results

Please make sure that the issue is reproducible on the vanilla Magento instance following Steps to reproduce. To deploy vanilla Magento instance on our environment, please, add a comment to the issue:

@magento-engcom-team give me 2.3-develop instance - upcoming 2.3.x release

For more details, please, review the Magento Contributor Assistant documentation.

@gwharton do you confirm that you was able to reproduce the issue on vanilla Magento instance following steps to reproduce?

• yes
• no

[m2-assistant]

Hi @engcom-backlog-nazar. Thank you for working on this issue.
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Hello @gwharton . We've been not able to reproduce Your issue following the steps Your provided. Herewith we attach three videos on how we were trying to do that. So please watch them carefully and tell us what we missed or did incorrectly there. Thank You.

[gwharton]

Can you view source on the email you received and compare a 2.2.7 and 2.2.8 email with the exact same settings.

I see your email client is recognising the email as UTF-8, but in the emails I receive, I don't see any headers that describe the body of the email as being UTF-8 encoded. My email client is set to auto detect encoding type, as most clients are by default.

Do you manually set your email client to UTF-8 or is it auto detecting UTF-8?

Here is what I see when I view source in 2.2.8. You can see the Subject and From fields are UTF-8 encoded, but there are no MIME headers, or any content type headers to tell the email client that the email is encoded in UTF-8.

Return-Path: <test@domain.com>
Received: by dev.domain.com (Postfix, from userid 33)
	id 7FD9AC16FB; Mon,  8 Apr 2019 21:34:39 +0100 (BST)
To: graham@domain.com
Subject: =?utf-8?Q?Newsletter=20subscription=20success?=
Date: Mon, 08 Apr 2019 20:34:39 +0000
From: =?utf-8?Q?Owner?= <test@domain.com>
Message-Id: <20190408203439.7FD9AC16FB@dev.domain.com>

You have been successfully subscribed to our newsletter. ö£€

Shouldn't there be headers like Content-Type: text/plain; charset=utf-8

Edit : If i manually change my email client to treat all incoming emails as Unicode instead of auto detecting, the email displays correctly. So, my comment stands, the missing Content-type header seems the culprit.

When viewing source, also notice that since 2.2.8 and 2.3.0 the following headers are also missing for plain text emails, hence me commenting, emails no longer sent as MIME.

Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
MIME-Version: 1.0

You can clearly see this in the source code. 2.2.7 and below used zf1 and 2.2.8/2.3.0 use zf2. In the 2.2.8/2.3.0 framework functions, plain text emails are sent completely raw with no headers. At a minimum i would expect to see content-type text/plain headers.

Take a look at the Zend Framework 1, setBodyText function below (part of zf1 library)

    public function setBodyText($txt, $charset = null, $encoding = Zend_Mime::ENCODING_QUOTEDPRINTABLE)
    {
        if ($charset === null) {
            $charset = $this->_charset;
        }

        $mp = new Zend_Mime_Part($txt);
        $mp->encoding = $encoding;
        $mp->type = Zend_Mime::TYPE_TEXT;
        $mp->disposition = Zend_Mime::DISPOSITION_INLINE;
        $mp->charset = $charset;

        $this->_bodyText = $mp;

        return $this;
}

Compare this to the newly implemented setBodyText function in 2.2.8/2.3.0 (implemented in Framework/Mail)

public function setBodyText($text)
    {
        $this->setMessageType(self::TYPE_TEXT);
        return $this->setBody($text);
    }

Prior to 2.2.8 using zf1, the setBodyText and setBodyHtml functions were almost identical. Both created a MIME email with the charcterset, disposition, encoding and type. The only difference between the two being the type set to either text/plain or text/html.

Now since 2.2.8/2.3.0, the setBodyText and setBodyHtml implemented in Framework/Mail functions are very different. setBodyHtml does the same as the original setBodyHtml did in zf1, but the setBodyText is vastly cut back, only setting the type. It does not set disposition, encoding, characterset or mime. Was this intentional, or did it just slip through because no-one tests using plain text emails?

[AlexWorking]

@gwharton the mail client we used is Crome browser if You mean That and we hadn't set manually any encoding related things. Here are the headers we've got:

(Magento version 2.3-develop)

[gwharton]

Yes, thats what I see too.

The email is missing the following headers

Content-Transfer-Encoding: quoted-printable
Content-Disposition: inline
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8

These are present in versions prior to 2.2.8, but are not present in plain text emails sent by 2.2.8+ or 2.3.0+

In the video you posted, there is a little drop down box on your email client which sets the email to "UTF-8". I believe this is forcing the email to be interpreted as UTF-8 encoded which forces it to be displayed correctly. Mozilla Thunderbird (and most other email clients i would imagine) attempt to automatically determine the content encoding type by looking for the content type email headers (which have been missing since 2.2.8/2.3.0 for plain text emails)

So, in response, I say you have reproduced the issue, its just that the email client you are using is forcing all emails to UTF-8, which is hiding the fact that the emails are missing these important headers.

If you repeat the test using version 2.2.7, and look at the email source headers, you will see the missing headers are present.