Requisition and PO Approval by email

Hi All,

We use email notification for Requisition and PO approval.

Currently we are moving the DB and application server from one location to another, and during this period there is going to be black out.

The DB and application server movement is not physically happening, but new servers are brought at the new location and refresh of the current production servers will be done.

The black out period is for 3 days. But during this 3 days of black out how can we prevent any user to click on the email approval notification mail for PO and requisition that might have got generated before the black out (but not approved) ?