I used to get around 50-60 emails a day. I am now getting less 5 or so. My email was hacked somehow. I changed the password. After the "hack" episode is when I started receiveing fewer emails. I have had friends send me emails that I am not recieving.
Check you auto-forward under settings (little cog in upper right). When someone hacks, they often change that so they receive any replies to emails they send.