Symfony version(s) affected

7.3 (probably all since 6.4)

Description

This is a bug report if the following from https://symfony.com/doc/current/mailer.html is a promise of behaviour:

Some mailer providers change the Message-Id when sending the email. The getMessageId() method from SentMessage always returns the final ID of the message - whether it's the original random ID generated by Symfony or a new one generated by the provider.

When sending via smtp, Sendermail discards the Message-ID generated by Symfony and sends one of its own. It also sends a slightly different X-MailerSend-MessageID header. It seems that if a message has two or more addressees, each one receives a copy with a different Message-ID but the same X-MailerSend-MessageID.

After sending, however, SentMessage->getMessageId() returns the id generated by symfony, which does not appear in the sent message in any form, nor in Sendermail's webhooks.

Symfony\Component\Mailer\Bridge\MailerSend\Transport\MailerSendSmtpTransport should pass its X-MailerSend-MessageID into the SentMessage.

How to reproduce

Set up a mailersend trial account, install symfony/mailer-send-mailer (7.3.x-dev@19c7b14 or later) send an email, examine the sent email's headers and the value of SentMessage->getMessageId

Possible Solution

When mailersend sends via smtp, the last line of the smtp dialog looks like

250 Message queued as 683f5db51040ad4bf570339c

That alphanumeric is the value Mailersend assigns to X-MailerSend-MessageID.

It will become the Message-Id of the SentMessage if line 160 of Symfony\Component\Mailer\Transport\Smtp\SmtpTransport is changed from
'/250 Ok:? queued as (?P<id>[A-Z0-9]+)\r?$/mis',
to
'/250 (Ok:?|Message) queued as (?P<id>[a-fA-Z0-9]+)\r?$/mis',