I too have friends who are like this. I used to get very irritated by the messages, especially when they have huge attachments. These days, I just see it as my friends’ way of keeping in touch. Kinda like the way Facebook users ‘poke’ each other for no reason other than to say hi. I don’t bother reading the mail, though.
I DO, however, respond when the message is one of those hoax emails that get propagated endlessly on the Internet and which are documented as being hoaxes on snopes or breakthechain.
If I know most or all of the recipients (e.g., the same circle of friends), I do a “reply-all” and tell everyone who received the message that they’ve been misinformed. The rest of the time, I just reply to the sender and advise them that they’ve been fooled by yet another email.
Now I get a lot less forwarded hoax messages, which is wonderful. But the forwarded jokes continue to come. haha!