1. Log in to exchange server with your admin credentials.
3. Log in to the Exchange Admin Center and click on Permissions.
Right-click ‘Organization Management’ and then click Edit.
Click the ‘+’ sign on the roles section. Select ‘Reset Password’ and then click Add. Click OK and then click Save.
4. Log out from the Exchange Admin Center.
5. When you log in again to the Exchange Admin Center and open any existing user mailbox properties, you should see the reset password option.