Not Recieving all my emails including ones for business reasons

Hello, I have had a  good look through the forums and I can't find an answer that works for my problem.  I am not receiving some emails that I used to have before.  They are not spam ones and they are inportant works ones that I am missing.  Whoever is sending them are not getting an error message from my email and I only know of a few I am missing but as noone is getting an error message I don't know how many people can't e mail me!  Help please!