Outlook Actionable Message header parameter „Authorization“

[RupertNold]

Dear experts,

can somebody help me with a technical question?

In an Outlook Actionable Message i have a button to do a POST to a http endpoint. The http service requires basic authentication with user and password. Normally I would supply the header parameter „Authorization“ with value „Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==“.

But Microsoft is overwriting this HTTP header parameter with the verification bearer token. When I use a empty value as „Authorization“ parameter, the verification bearer token is moved to the „Action-Authorization“ header parameter. But the bearer token is not moved to the „Action-Authorization“ header if I supply a concrete value.

How can I provide the basic authentication for the http endpoint?

https://learn.microsoft.com/en-us/outlook/actionable-messages/security-requirements#verifying-that-requests-come-from-microsoft

https://learn.microsoft.com/en-us/outlook/actionable-messages/security-requirements#action-authorization-header