An email offer just went out: AMEX Marriott co-branded cards can now enroll in a promotion to earn 10x points on purchases made with PayPal at merchants (2x base points + 8x bonus points), up to 50,000 points total. The offer ends on December 31.
The terms do say that certain transactions do not qualify, so use your own judgment.
Eligible purchases means purchases for goods and services minus returns and other credits. Eligible purchases do NOT include fees or interest charges, cash advances, purchases of traveler's checks, person-to-person payments, the purchase or reloading of prepaid cards, and purchases of other cash equivalents. Additional terms and restrictions apply. Points received from your Card will be posted to your Marriott Bonvoy member account up to 12 weeks after the end of each month. To be eligible to receive points, Card Member’s account must not be cancelled or in default at the time of bonus fulfillment. Points may appear on your account in more than one deposit. Points may be reversed if the eligible purchase is returned.