Email disappearing from Outlook 2013 using O365

Using Outlook 2013 with Office365. Large groups of email are missing. In the inbox sorted by date descending there a re big gaps of mail missing. Last month had quite a bit missing, more missing from the month before, then large gaps of many months with no email at all, then some from a year ago, then some from a couple years ago. Did the restore deleted items from the inbox and that restored a lot (mostly recent from the last couple of months)

Also receive this same O365 account to an Iphone and an Ipad.

I suspect it might be IOS device since I had a similar problem a while ago but in that case you could watch the email go away.

Any suggestions would be greatly appreciated.

Thank You
Bob