It’s a really bad idea. Plastiq has your billing address from your credit card. If you try to send a check to yourself, Plastiq can put two and two together. Many churners have tried and got caught. A lot of times, it’s a stern email saying payments to yourself or individuals are prohibited, but you do not want to draw attention to your account or ruin this service for yourself.
What you’re suggesting is essentially manufactured spending (“MS”), which Plastiq does not allow. If you send a payment to yourself, there’s nothing Plastiq can do to make sure you don’t just deposit their check into your account to pay off the bill for the credit card that you used to fund the payment in the first place. Many credit card agreements also prohibit activities that can be described as MS. Plastiq makes a lot of effort to prevent and catch MS, comply with credit card guidelines, and basically stay legit with the credit card networks they process their payments on. We all benefit from this because when a Plastiq charge posts to our credit cards, it’s presumed legitimate, earns points and counts towards MSR.
Now, you might be thinking, what’s the difference between paying yourself, which is prohibited by Plastiq and the credit card companies, and finding a workaround to paying your mortgage, which is prohibited by Visa and Amex? Plausible deniability on the latter. Plastiq supports mortgage payments on Mastercards and Discover, and the process for setting up a payment is the same as for Visa and Amex. Since there’s no uniform way to set up a new Recipient, you might just have formatted it in such a way that doesn’t exactly match what Plastiq has for that mortgage company that you can’t pay with a Visa or Amex. If it slips through, it was a simple mistake; if it doesn’t work or is caught later on, now you know and it was always YMMV.