PHP Sendmail email priority?

Question

PHP

Problem: when launching a newsletter to users, it clogs the entire sending queue and registration letters leave with a delay.
Is there any way to set the priority when sending emails via PHP? So that registration letters go “without a queue”?
Maybe Sendmail respects X-Priority?

Answer 1

In short, the answer was found in the Sendmail book.
You need to set the Precedence header for letters.
I have set Precedence: junk to the mailing list. Now the rest of the letters now leave immediately, and the mailing list is “in the background”.
The default classes are: first-class, special-delivery, list, bulk, junk - in descending order of priority. You can set your own.
You may need to set QueueSortOrder=priority in the sendmail config and increase the ClassFactor.

Answer 2

maybe it makes sense to send the newsletter through another relay?