Change or specify value of a header Using Exchange Online

[tcboeira]

Using Exchange Online exclusively, is it possible to change or specify a value for a header? For example:

X-MS-Exchange-Organization-Original-Sender
or
X-MS-Exchange-Organization-AuthAs

In fact, the objective is to see who actually sent a message through a shared box or a distribution list.

[#2]

You can use the audit log to answer that question.

You can examine and modify (a limited set of) headers via mail flow rules, but they will not help you with messages that were already sent.

[#3]

@VasilMichev , Thanks for the answer...

So that means... Someone who sends a message through a Shared Box OR a Distribution List, the recipient doesn't know who did it by reading the header.

As Environment Administrator, I can obtain this information through the Audit Log.

And... Sorry if it seems like too much... But, it commented that a limited number of headers I could change per transport rules.

The documentation suggests - generally - something aimed at On primese/Exchange Local. Not for Exchange Online. Would that be it? Are these changes not possible for Exchange Online?

And where could I get what header I can change?

[#4 · Accepted solution]

I don't think I've seen a list of headers you can modify. In general you cannot touch any of the "transport" ones, but can make changes to headers used by various other features (i.e. modify SCL, apply/remove label, focused inbox one, etc).