I throw away queries without SASEs.
I've taken some heat for that.
If you think I'm being a hardass for this, so be it. But consider this: I emailed someone about five seconds ago asking for the first three chapters. Yes, I have his SASE. Yes I'll probably use it to say no after I've read the first three chapters (remember, this isn't a comment on his writing, it's a reflection of the 1% yes rate right now).
His email bounced. I can't tell why. It may be that eye and one are transposed, or there's a typo on his query letter. Who knows. I'll use the SASE t ask for chapters now, but if he had not included it, he'd never hear from me even though I tried.
This happens more than you think. When I type in an email address there are three critical chances for error: you have to make sure you don't have a typo; that you have an email address that's not subject to easy error; and that I type it correctly. If you assume that every email sent to you gets to you, you're the firstname.lastname@example.org
Electronic communication isn't foolproof.
Neither is snail mail.
Putting your email address on your query letter is a very very good idea.
So is including an SASE.
Mr X has no idea how smart he was to do this.