1. Press the Windows key + R and type regedit. Click OK.
2. In the left pane of Registry Editor, navigate here:
HKEY_CURRENT_USER\Software\Policies\Microsoft
3. In the left pane of above mentioned location, right click Microsoft key and select New -> Key. Name the newly created key as Office. Similarly create sub-key 16.0 if you’re on Office 2019 or 15.0 if you’re on Office 2013 to Office key. Again create sub-key to 16.0 and name it Outlook. Moving on, similarly create sub-key to Outlook and name it DisabledCmdBarItemsList. So when you highlight DisabledCmdBarItemsList key, you must be at HKEY_CURRENT_USER\Software\Policies\Microsoft\Office\15.0\Outlook\DisabledCmdBarItemsList. Now come to the right pane of this registry location.

4. In the right pane, right click and select New -> String Value. Rename this newly created registry string (REG_STRING) as TCID1 and double click it. Put the Value data as 20103 now and click OK. Finally, close Registry Editor and restart your system. After reboot, you’ll be able to find Delegate Access option on the start page of Outlook application.