I've set up my email program to not respond to requests for notification of any kind. I use the Spaminator program from Earthlink, and the way that one works best is if you DO open the spam, just long enough to do a control-H (open the header), control-A (select all), control-c (copy) then paste it into a blank mail to go to spaminator. It gets added to what they filter out. It goes in spurts, working most of the time, then some new server comes on line and starts getting past the spam filter all over again.
I have had a rule of thumb about the spam I open, and anything over about 25K I don't open. But I just read through the stuff at Symantec and see that some of these viruses can go in the body of the message. It may now be time to delete all with out forwarding.
A question: is there a rule of thumb to take bytes to K? Is it a simple matter of decimal points? It isn't helpful if Symantec tells me that a given virus will appear as 143,360 bytes if my email only reports my message size to me as K. Should I look at the above number as the same as 143K? Or 14K? Or something close to a megabyte and a half at 1433K? I used to know how to do this, but I remember there was some squirrely stuff involved with translating some of these numbers.