Easy enough to send emails with Symfony + SymfonyMailer messages out. The issue was once received in a program like Outlook, how do you group them into the same conversation.
Instead of flooding an inbox with a ton of emails, the emails would be grouped by conversation.
To accomplish this:
<?php // in the __constructor, autowire MailerInterface into $this->mailer $subject = "something"; $somethingHashedThatRepresentsThisConversation = "someHash"; $messageId = "$somethingHashedThatRepresentsThisConversation@domain.tld"; $email = (new Email())->from('firstname.lastname@example.org') ->to($targetEmail) ->subject($subject) ->html($html) ->text(strip_tags($html)); $headers = $email->getHeaders(); $headers->addIdHeader('Message-ID', $messageId); // Original Message ID, I've found reusing it workss. $headers->addIdHeader('References', $messageId); // Original MEssage ID to group by... could add others... I've found that this can reference itself. $email->setHeaders($headers); $this->mailer->send($email);
There you go.
PHP 8.0.x, Symfony 5.3