Email from person in contact list being occasionally blocked

I have person in my contact list that is sending email that occasionally I'm not receiving.  He has been sending me the same email to another email address, and I always get the email there, but only occasionally receive the email in my hotmail/outlook.com mailbox.  He is in my contact list, added to my safe email filter, and it does not appear in the Junk folder.  Am I missing something?  Is there another area it could be getting blocked?  It is my daughter's soccer coach, and the irony is I more often receive the email when it is sent as a group email than when he emails me separately...  Any help would be appreciated...