Spoofing problem

There are lots of articles about spam and spoofing but as yet I can not see a cure for my problem. Lately I get many emails each day with ads, the sender is my own email address which means I can,t blacklist it.
My ISP is of no help anf just refers me to on line articles about the problem. My computer has not been hacked and is clear of problems, any are picked up by Bitdefender ?

We made this announcement some years back, which describes how eM Client is not vulnerable to spoofing:

I can see and tick on “Show email address in header” but can,t find show “Display name only”