Mail.app and spam - a way around tipping them off?

[rusto]

I recieved an email today that might or might not have been spam, it was sufficiently ambiguous that I really wanted to look at it but, if it was a spammer, did not want to tip them off that my email address was valid by actually looking at it.

So, without opening it, I just hit "Reply" which revealed the contents of the email to me (as it turns out, it wasn't spam). The original email remained marked as unread in my Inbox.

Is there a way to know if this technique (using "reply" without actually sending a reply as a way to view suspect email), if used on a piece of spam would prevent the spammer from noticing that it was read?