How to block e-mail that comes from McAfee or Norton.

Almost impossible because the points of origin are spoofed and change constantly. You can try to block the Subject line and that may help if Norton, McAfee, or Geek Squad is listed. But even then, if they change

from a capital to lower case letter, adding a space, another character etc. the the filter won't work.

All you can do is keep flagging them as spam and hope the spam filters work. Whoever sends these must have figured out yahoo’s spam filter because the mcafee and norton emails are just about the only ones that don’t go to the spam folder. The strange thing is that when I get one in my inbox, there will be 2-3 others that did go to the spam folder.