Email: legitimate duplicate email header keys with mutually exclusive values

Question

In email the Received: header can legitimately occur more than once with mutually exclusive values...

Received: three.example.com

Received: two.example.com

Received: one.example.com

Are there any other headers can occur in email headers multiple times legitimately?

score 8 · Accepted Answer · edited Oct 07 '21 at 05:51

8

Ya there are other headers that can appear more than once and is clearly explained here in RFC 5322

Headers that can appear more than once

Check the link above for more clarity.

edited Oct 07 '21 at 05:51

Community

answered Aug 04 '13 at 06:22

clement

3

Note that "optional-field" is basically any field not defined in that particular RFC. – Arild Dec 08 '14 at 10:48

1 Answers1