External federated contacts don’t appear in Teams search
If you have imported contacts from a federated partner tenant into Azure Active Directory (Azure AD) or Exchange Online, the contacts might not appear in Microsoft Teams contact searches.
This problem occurs because Teams uses contacts in your organization’s Active Directory and contacts that are added to your Outlook default folder.
Searching in Teams for external federated contacts is supported only under the following conditions:
Your mailbox is hosted through Exchange Online, not Microsoft Exchange Server on-premises.
The external contact phone number is included in the contact information.
You search for the external contact by email address, not the contact name.
Note Although it is not supported, searching for an external federated contact might work if the contact is currently cached on the client computer.
If these three conditions are met, external federated contacts will appear in searches.
In Teams, you can communicate with anyone in your organization’s Active Directory. You can add anyone as a contact in Teams by selecting Calls, selecting the Contacts tab, and then selecting Add contact.
For more information about how Teams and Exchange work together, see How Exchange and Microsoft Teams interact.