MassPay can include up to 250 payments per request. You must have a PayPal balance
with sufficient funds to cover the entire Mass Payment amount and fee. You cannot
mix currencies in the same MassPay request.
Insert a few MassPay Items into the list and submit the payments to make the MassPay request.
Payments can be made by email address or PayPal User ID, but the whole set must be
sent the same way.
MassPay triggers the sending of an Instant Payment Notification. You must check the
IPN to get the necessary information you need about the transaction.