Plastiq has a promo going on until the end of September (so 2 more months) where if you use MasterPass to pay, the payment is fee free up to $250 (and 2.5% fee for whatever amount over $250), so a lot of people have been making payments in $250 increments to their mortgage companies, student loans, etc. I believe you can only schedule 1x $250 payment a day, but some people get around this by scheduling payments for $249.97, $249.98, $249.99, $250, etc.
DPs say adding MCGCs to MasterPass works for payments through Plastiq. Churningsearch is down so I’m having a hard time digging up more DPs. Obviously, with Chase Freedom and Walgreens there’s one way to get a $500 MCGC for 5x and offset the 1.19% fee, and Amex’s Lowe’s and Staples offers give 10% statement credit on MCGCs and their fee, even though those max out at $200 and has like a ~3% fee. But the point is to meet MSR on new Amex cards, so the most straightforward plan would seem to be to buy $500 MCGCs from a store that doesn’t report level 3 data, like a grocery store, for a $5.95 fee (1.19%), add to MasterPass, and liquidate that card through Plastiq in 2x fee free payments of $250. (Which is better than Plastiq’s standard 2.5% fee, considering the Plat doesn’t code in any way that offsets the 2.5% fee, and MasterCards don’t have the restrictions that Amex has.) Rinse and repeat.
Before making payments to a mortgage in $250 increments, you should probably find out how they treat partial payments and overpayments, like whether it’ll apply against your monthly payment or against principal only.