OK, now this is very odd... enclosing picture... 

in the certificate tab I have that problem (and on the email of course when I try to connect), however in the automatic certificate tab it seems ok.

There is a JSon file... should I deactivate the ssl, delete the jason file and repopulate the ssl?

I only have a handful of domains so I can do updates in DNS if I have to update the keys.

But also in the bindings. I use Let's encrypt certificates for the binding in IIS for any domainX.com and www.domainX.com on port 443.

In smartermail I set up certicficates requests for the following prefixes only:

Anything I am doing wrong?

I wonder if the mismatch between the renewal date/expiration date is a byproduct of the move perhaps. Maybe you're getting data from both the new and old renewal procedures depending on the hostname you're looking at. I don't recommend deleting the JSON and repopulating it, this could lead to a large number of LE requests going out to renew/request certificates which could lead to you hitting some rate limiting. Can you submit a ticket on this so we can take a closer look please?