Press Windows+R Key then Type regedit & Hit Enter key

Select Yes

Now follow the steps:-

Click on HKEY_CURRENT_USER

Click on Software

Click on Microsoft

Click on Windows

Click on CurrentVersion

then
Click on Policies

If the Attachments key is absent then right-click on the Policies key, click New then select key and name it as Attachments

Select Attachments key

Right-click here, Click New and then select DWORD (32-bit) Value and name it as ScanWithAntiVirus

Double-click on the newly created ScanWithAntivirus and change it's value data to 1 to disable the Attachment Manager

Now Close the Registry Editor, Save your work and restart your computer to apply the change

To Enable the Attachment Manager VIA Registry

Press Windows+R Key then Type regedit & Hit Enter key

Follow the path: open the same location

HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Attachments

Double-click on ScanWithAntivirus and change it's value from 1 to 3

You can also Turn on or off Attachment Manager via Group Policy

Press Windows+R key to open run command box then type gpedit.msc & HIT Enter key

Now navigate to:

User Configuration > Administrative Templates > Windows Components > Attachment Manager

Double-click on the Do not preserve zone information in file attachments
Select Enabled option then Click Apply button to save the change

It's Done..

if you want to Disable it select not configured then apply & OK