Not receiving some emails from a particular email address

Not receiving some emails from a particular email address

I am not receiving emails from a particular email account. The problem is that I receive some of the mails sent from that account (roughly every third email) but other mails never reach my inbox (or junk folder or any other folder for that matter). 

Please let me know where and how to intimate you about that particular sender's email id (privately). 

Best regards,
Pankaj