Not receiving some emails

 starting a couple months ago I stopped receiving some emails,  Some where from emails that I was receiving from before and some where new contacts trying to reach me.   If I found out from someone that I was not responding to emails I had to add them to the safe sender list.  Otherwise  I have no idea how many potential clients I have lost.  I have been in contact with out look with each response taking at least 24 hours.   so far  they had me check all the normal stuff,  rules, spam, reset the allowed devices etc.  with no change.  I have left a couple emails off of my safe sender so that we can test the issue.  even have checked blocked emails.   no solution.  I need help and cant find a way to call for help.