I don't know if there is a particular certification for any IMAP supporting email system.
But how is your domain setup? Do you have an admin sever domain, that is cloned to a managed server domain folder, from where the managed server is running? So, basically, is your SOA Server running from another domain folder than your AdminServer? Then you might hit the problem described here: https://blog.darwin-it.nl/2018/10/persisting-of-settings-in-soa-suite.html It might be that your
After doing your UMS settigns, bring down the SOA Servers and the AdminServer. Check the driverconfig.xml from the Managed Server domain, and copy it back to the Admin Server domain. And bring the servers up again. It doesn't completely explain your problems, but I'd check the driverconfig.xml file first. Maybe some of the properties didn't get propagated properly.