We are running W2019 as well as W2022 - both without problems, the 2022 edition is running a bit more smooth but no big difference.
But why not changing to the Linux version?
Especially if the Windows server is serving nothing else than Smartermail.
We migrated a bunch of machines from Windows to Linux -
setting up the Linux box, configuring SmarterMail and then detach+attach the domains (works great).
All Linux instances are running very fast + stable, no problems.
And ... the update process is very fast and there were a lot of updates in the last months.