Can custom email headers trigger spam filters?

Question

We do a lot of mailing, and we use Sendgrid to give it unique arguments and categories. But for storage, archiving, filtering and searching, I would also like to give them some other custom headers, something like the json format of this array

array('user' => 300, 'item' => 8842, 'country' => 'Croatia'); 

Now, is it possible for such custom headers to hinder the end-to-end speed of our emails? In other words, is it likely that our emails will trigger spam filters due to the presence of such custom headers?

Answer 1

The convention for custom headers is to prefix them with X- . for instance

 X-my-custom-header: foo 

This has long been part of the email specification (see http://tools.ietf.org/html/rfc822 ) and should never have hurt your enforceability.

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