Sometimes, you may need to add or remove certain fields to Outlook contact cards such as Mobile number, Address, …
These fields are managed by the Global Address List (GAL). In order to make changes in the Global Address List, you must use the Details Template Editor located in the Exchange Toolbox MMC.
Go to your Exchange server, and open the Details Template Editor

Locate the details for English Users for example, and double-click the en-US\Usertemplate

Select the field you want to remove and press DELETE. Save this form: File -> Save

Now, wait a moment to replicate the changes then close and reopen your Outlook.
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