Unfortunately it is currently only possible to reprint Remittance Advices individually.
There is no built in function to resend a Remittance Advice via email, but some of the below suggestions may help:
For a small number, you could save the reprinted Remittance Advise 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, you could unallocate the payments and then 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.