I've been using iCloud for my personal email for a few years and have never had an issue. In fact, I've never lost a single piece of data with iCloud, but I'm still hesitant to trust it like I trust Dropbox.
I used a corporate Outlook email system for many years. All worked fine until I retired and tried importing my outlook contacts into Apple - absolute disaster that ended up with me pretty much having to re-enter all my contact data! My advice: avoid Outlook and go for iCloud.
PS: Dont underestimate the challenge of transferring the "auto-complete" email addresses from your gmail account!! It ain't straightforward!