Outlook removes custom X - header?

[ron79]

Hi @ all,

It seems that outlook deletes my custom X - header when
answering e-mails.

However, i know of other custom headers which Outlook
does not touch, i.e.:

X-WW-Spam-Likelihood: Bayesian=5, BodyRules=50, DBL=50,
Mailshell=51, total=5

My one looks like this:

X-MailNumberID: - DA: XXXX|KR|1968533910 -

What makes the difference?

regards, ron