In my Canadian version, I can send the remittance slip via email ONLY if I pay out the bank account.  If I choose a credit card payment it will not allow me to send the remittance slip.

My work around is,  I save the remittance as though it is paid from the bank account and then go back in and change it to a credit card payment.  It is a pain, which ever way you look at it.  

1.  First of all,  you should not have to save it and then go back in, find the payment and then send it

2. Secondly, remittance slips should be email enabled no matter what kind of payment is selected.