We completed a cut over migration to Exchange online some time ago and all mail is flowing only via O365. We use Azure AD Connect to keep on-prem and Azure user accounts synced and so have retained the on-prem Exchange 2010 server running on Windows 2008 R2, purely to manage the email user attributes and distribution list, as recommended. All mailbox contents have been deleted to save space, just the mailbox themselves exist.
I'm not happy about keeping such old, unsupported servers and I'd like to upgrade to supported platforms, Exchange 2016 and Server 2016 at least.
1. Is this necessary, or am I OK keeping running the old server, given there is no longer any connection to the internet from it?
2. If necessary, is there a simple guide to upgrade, given the server isn't actually going to do any work? Lots of the online guides I have found are very involved, given all I want is to retain the management of the email attributes.