This post assumes you are married (or living with a partner, fiance, etc.), and that your mortgage is over $1,000.00 a month.

If the above applies, get two Serve cards, one for you and one for your spouse/partner, etc. On the first of each month, load the max amount possible onto each card ($1,000 per card, $2,000 total across both cards) using your credit card (note that you will need two different credit cards -- your spouse/partner cannot use the same credit card as an authorized user to load the Serve card).

Once you have funded your Serve cards, you can use the bill pay feature to pay your mortgage. Most banks (I know Wells Fargo allows it) will allow you to send 2 checks as a mortgage payment. Send the checks on the same day via Serve, and in the For/RE line, indicate your account number and clearly state "JULY 2014 - PMT OF PRINCIPLE & INT."

This only works on non-AMEX cards to the best of my knowledge.