Check you SPAM folders!!
In a targeted email, United is offering discounts for mile purchases until May 31.
The terms of the promo:
Buy 20,000 or more miles and receive 25% off.
Buy up to 20,000 miles and receive 20% off.
Though it may not be the best miles sale ever, 20-25% is still a good deal if you are “just short” of enough miles for that coveted Business or First Class ticket.