Mailer improvement

[FlashPanther]

Sylius version affected: 1.7.6

Description
The mails sent by sylius do not seem to be of the best quality.
The "text / plain" element and the "list-unsubscribe" link are missing.

Steps to reproduce
Just register and open your mail box

Possible Solution
Modify Bundle/Sender/Adapter/SwiftMailerAdapter.php

[patrickallaert]

In order to decrease the chance of being considered as spam, we should absolutely be able to send email with a text/plain part in addition to the HTML one.
Currently, there is no way we can achieve that without completely hacking the core of Sylius.

[lchrusciel]

Hey, thanks for pointing it out 👍