Add external address book to Outlook 365

Tim Schmidt 1 Reputation point

I want to add an address book to Outlook, which contains external addresses.
I've read that you need MAPI to develop an address book provider, which then would handle the external addresses.

The problem is that I can't find the MAPI headers for developing the provider. The Links I found on the platform are all broken. #

In this question, it's stated that my goal is only achievable with MAPI, but it's 10 years old. Therefor, I have two questions:

  1. Can I find the MAPI header files anywhere?
  2. Is there any alternative to add an address book without adding the addresses to the user's local contacts and without MAPI now (hopefully in C#)?
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  1. Vasil Michev 96,436 Reputation points MVP

    What's the end goal here? Populate some contact entries that are accessible company-wide? If so, probably the best option is to create a new Address list, which will automatically appear in Outlook and can be selected under the Address book dialog. Read here: