Exchange 2013 - User receiving delegated meeting notifications from other users

So, I have a user (UserA) that was at one point a delegate for two users. User1 and User2.

UserA is receiving email notifications from both User1 and User2 about meeting invites etc (as if she was a delegate to these users).

Neither User1 nor User2 have UserA listed as a delegate (if I check File - Account Settings - Delegate Access, this list is blank)

So I thought I'd attempt to wipe all delegates from User1 and User2 and applied this to both User1 and User2:

Get-Mailbox -anr "User1" | Get-CalendarProcessing | select ResourceDelegates 

Get-Mailbox -identity "User1" | Set-CalendarProcessing -ResourceDelegates $null

It seems UserA is no longer a delegate for either user, yet UserA still receives notification emails from both users as if she still is a delegate...

Any idea's where else these settings should come from?