Postmark doesn't preserve Message-ID and In-Reply-To headers

[csaftoiu]

If I deliver a message with postmark, the message-id and in-reply-to headers aren't preserved.

I tested sending the same message, but with smtp delivery, and the headers were preserved on the yahoo groups interface - so it isn't yahoo that is changing them. The SMTP method does indeed preserve topics even with different subjects:

We'll need to figure this out in order to be able to send threaded messages with postmark. Until then, SMTP delivery from Heroku should work - at least, I tested it via heroku run bash and it worked, will see if the scheduled task delivers it also.

[srid]

Alternatively we could try one of the other email add-ons like SendGrid or Mailgun.