2726291 - Error Message:E-mail address is invalid: Not listed in allowed email domain

When last approver tries to approve the Purchase order you get the above error.

or

You have created a new purchase order however system shows the error message when you click on order button.

 or

When you try to navigate the document flow of the purchase order, system crashes.

 or

 In the edit output settings  of purchase order  click on apply, you will see same error

SAP Business ByDesign

E-mail address is invalid: Not listed in allowed email domain,  Purchase order Out history is empty,Purchase order Output not generated,invalid e-mail address: not listed in authorized e-mail domain , KBA , AP-POP-PO , Purchase Order , Problem