14

According to Google Mail guidelines, bulk mail must contain the header 

Precedence: bulk

What does it do? I could not find a RFC describing the effect on mail delivery.

Some background: I'm working on scripts that will send 500k+ mails daily. They are different kind of messages: account related mail (delivery critical), but also notifications of new content (delivery not critical).

Mark Amery
  • 143,130
  • 81
  • 406
  • 459
Ward Bekker
  • 6,316
  • 9
  • 38
  • 61
  • You might also find interesting the document linked to from my answer here: http://stackoverflow.com/questions/4175433/princibles-on-how-to-send-a-mass-mailer-without-it-ending-up-in-junk-mail – SimonJ Jun 05 '11 at 00:02
  • The linked Google Mail guideslines no longer recommend use `Precedence: bulk`. – Richard Michael Feb 17 '22 at 01:26

2 Answers2

14

The exact meaning of Precedence: isn't standardised, but it prevents some mail servers from sending vacation and bounce messages, and may be used by service providers to deprioritise bulk mail during busy times so that "personal" mail continues to be delivered quickly.

From RFC2076:

Non-standard, controversial, discouraged. Sometimes used as a priority value which can influence transmission speed and delivery. Common values are "bulk" and "first-class". Other uses is to control automatic replies and to control return-of-content facilities, and to stop mailing list loops.

Community
  • 1
  • 1
SimonJ
  • 21,076
  • 1
  • 35
  • 50
4

See the answers to this question, as well as RFC 3834.

In short, the Precedence: header is non-standard. Google's recommendation is perhaps just a way to give a hint to their spam filters that you really did intend to send out 500k+ emails from your server (as opposed to one abused by spammers).

Mark Amery
  • 143,130
  • 81
  • 406
  • 459
spacehunt
  • 803
  • 5
  • 8