Symfony version(s) affected

5.4

Description

When an email is sent through the messenger using alternative mail transport and if this mail transport fails then modified email is pushed to the queue for the next try (without X-Transport header). The second try takes default mail transport whether you want it or not.

How to reproduce

https://github.com/Nommyde/mailer-messenger-bug

run:

php bin/console app:send-email -vvv              # an email pushed to the queue
php bin/console mes:consume async --limit=1 -vvv # error on the second transport
php bin/console mes:consume async --limit=1 -vvv # success on the first transport

Possible Solution

In this case I believe the method \Symfony\Component\Mailer\Transport\Transports::send should clone a message before modifying and sending it.

Additional Context

No response