we are in a hybrid O365 and on premise exchange exchange (2016). And i am seeing that all external contacts that we add end up with additional "other email addresses" besides the correct (external primary address). The other addresses end with our domain.
Ex. Josmith@abccompany.com will be shown as the primary email - external contact
in the email options however I will see something like this, email@example.com and firstname.lastname@example.org
The problem now is that if i need to add an internal user that's named email@example.com it does not work. It will tell me that josmith@mycompany is already in use.
how do I fix this problem? I can't delete the external contact.