membershipEmail
The membershipEmail element is an optional child of the customerInfo element, but required for Guaranteed Payments. It defines the  email address associated with the membership. If the customer is not enrolled in your membership program or is checking out as a guest, you must send this element with a null value.
Type = String; minLength = N/A; maxLength = 100
Parent Elements:
Attributes:
None
Child Elements:=
None