Backup, Restore, or Transfer Email VIP List

Whenever I upgrade to a new iPhone, I transfer all my data using iTunes Backup/Restore. For the most part it always goes smoothly (although my most recent one didn't transfer any music for some reason). The one issue I have is that I always lose my email VIP List and have to re-enter every contact I want as a VIP.

I use the stock IOS Mail app, but I use Office 365 for cloud storage (not iCloud). I'm guessing that might be the cause, but it still isn't completely clear because I also have a VIP list in the Phone app, and that transfers over just fine.

Is anyone else seeing this?

Does the Email VIP List get transferred correctly when using iCloud for Contacts?

Is it possible to backup or somehow sync the Email VIP List if you use Office 365, or Exchange, or Google, etc?

Why would Phone VIPs be restored properly but Email VIPs (using the same Contacts) are not?

Most recent transfer was iPhone 6s (IOS 11.4) to iPhone Xs (IOS 12)

Thanks:)