Mime parts of email are no more encoded with quoted printable

[ffauvel]

Preconditions (*)

1. 2.2.8+

Steps to reproduce (*)

1. Add a lot of css to the email template
2. Complete an order

Expected result (*)

1. The email is sent to the customer

Actual result (*)

1. The email is rejected by the mail server - Error message: Message too big

Before 2.2.8, Magento was using Zend_Mail and Zend_Mime_Part (from ZF1) to send email.
The default encoding of Zend_Mime_Part was QUOTED_PRINTABLE.
In Magento 2.2.8+, they switch to Zend\Mail (from ZF2). The default encoding is 8bit.

It should be change back to QUOTED_PRINTABLE to avoid overlong lines.

[m2-assistant]

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

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• 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 give me 2.3-develop instance - upcoming 2.3.x release

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

• yes
• no

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[ffauvel]

@magento give me 2.3-develop instance

[magento-engcom-team]

Hi @ffauvel. Thank you for your request. I'm working on Magento 2.3-develop instance for you

[magento-engcom-team]

Hi @ffauvel, here is your Magento instance.
Admin access: https://i-23643-2-3-develop.instances.magento-community.engineering/admin
Login: admin Password: 123123q
Instance will be terminated in up to 3 hours.

[m2-assistant]

Hi @gwharton. Thank you for working on this issue.
In order to make sure that issue has enough information and ready for development, please read and check the following instruction: 👇

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[magento-engcom-team]

Hi @ffauvel. Thank you for your report.
The issue has been fixed in #23650 by @gwharton in 2.2-develop branch
Related commit(s):

• 9f66582a354fc57e7931cd1fbdf73d874f25baf2

The fix will be available with the upcoming 2.2.10 release.