Remittance Advices can only be reprinted individually.
There is no built-in function to resend a Remittance Advice by email. The following workarounds may help:
For a small number, you could save the reprinted Remittance Advice as a PDF document using the Export button on the window showing the Remittance Advice and then manually send this PDF file to your supplier.
For a larger batch, unallocate the payments and reprocess the remittance batch to send the emails.
You would then need to post a reversal of the unallocated payments and allocate it against the original.
The Import grid may help to speed this process up.