The government owned postal service did that where I live. They went from deliveries every weekday to every other weekday, so some weeks you get post twice and some thrice.

It works pretty well and I haven’t really noticed any negatives. First class parcels and express mail are still delivered every weekday. Normal letters get delayed slightly but that doesn’t really matter because you rarely get mail anyways and it’s never that time critical.

The only mail that most get are from government agencies and you can get that delivered digitally nowadays.