Stopped receiving email notifications after years of getting them.

I am unable to receive email notifications of any kind after years of getting them. I use them to track file access by my non-profit volunteers. I have checked all email settings, all notification settings and made sure any and all possible box senders and domains are added to my safe senders list, turned notifications off and back on etc. I hate to complain as a free account is way more than enough for my needs, but if there is any advice available I'll take it!