I often find that my single character local address fails, and I need to add a plus something. e.g. x@familyname.com is rejected, but x+whydidyourejectthis@fam

I often find that my single character local address fails, and I need to add a plus something. e.g. x@familyname.com is rejected, but x+whydidyourejectthis@familyname.com works