Benign Email Headers

Question

On our server, we have two separate email systems: if it's a long queue of recipients, then we store it in a queue to be sent in a cron. If it's less than X number of recipients, then it sends immediately. Both are built in PHP with MySQL storing the queue.

However, there is a question of whether or not this is working 100%. In order to determine which email system is sending the email, I'd like to add a simple, completely meaningless email header like foo:bar or something like that.

So, my question is: is this at all possible? Would a foo:bar email header screw anything up? I'm not very well versed on what's under the hood, here and it's a live system sending out thousands of emails per hour.

I'd just like to be 100% certain that this is not only possible, but will be completely benign. Google was returning results about unsafe email headers, and I wanted to know if there will be problems just passing foo:bar. — Phoenix Rising, Apr 15 '15 at 17:43

score 3 · Accepted Answer · edited Oct 07 '21 at 06:58

3

Adding some X-Foo: cron header (with the X- prefix!) isn't a problem, you can add them as you like.

Edit

I forgot about https://www.rfc-editor.org/rfc/rfc6648. So scrap the X- part.

edited Oct 07 '21 at 06:58

Community

1

answered Apr 15 '15 at 17:47

Sven

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The only issue I'm aware of with adding more distinct header lines is the per-mail database limit in some versions of Exchange (see for example http://serverfault.com/questions/130624/how-can-i-determine-which-named-property-or-properties-are-filling-my-exchange). – Paul Haldane Apr 15 '15 at 22:11

Benign Email Headers

1 Answers1