Hello and good afternoon. This is my opinion, but it does originate from the support department! My personal recommendation on this would be to attempt a test upgrade of your servers in a dev/test environment to give you the opportunity to test before you roll this out to production. To move a copy of your domains to a new server for testing purposes you can use the KB article linked here:
Once you've completed your test upgrade, you can check on the status of the domain conversions by navigating to the link below (modified for your hostname):
If this completes successfully in your test environment you should be good to upgrade in production! With that being said, you can ensure a smooth upgrade with a couple of steps taken beforehand:
1. Pre-install .NET 4.7.2 (or the latest available) on the server to shorten the install time required.
2. Set up a backup MX with a free SmarterMail install to handle incoming mail spooling until the primary comes back online.
3. Take a full backup of the installation directory and domains, and don't panic! With a proper backup anything can be reverted safely.
As always if you need any help along the way - we're here for you - and would be happy to help get you on to the new version. On that front, planning your upgrade during our business hours definitely helps ensure someone is available to support you, but we also have emergency support available should you need help in the middle of the night. If you have any outstanding questions, or see anything I missed in my response please let me know.
Kyle Kerst
Technical Support Specialist
SmarterTools Inc.
(877) 357-6278
www.smartertools.com