I wonder what is happening to your national mail system?
In my small village in the South of France, there is sporadic delivery of mail. The local Post Office is closed, and people are directed to one about 10 miles away -- but there is a 'lockdown' on almost all travel, and it's far from clear that a trip to this Post Office to send off some Mail Art would be accepted by the authorities (and, if not, would result in a €135/$150 fine).
The only shop that sells stamps in the village has sold out of them and doesn't know when, or if, it will get some more.
So mail comes in sometimes, but it's very difficult to send Mail -- Art or otherwise -- out.
The lockdown is initially for 2 weeks, but methinks that this is a very optimistic time-frame indeed.