What type of phone are you using? With standard messaging apps, I don't recall there being a way to do this. I have an iPhone and have had this happen a few times. When it does, I go through the Messaging app, select the message that came from the email address, view the contact's profile card and block from there. The only downside to going this route is spammers will use so many different email address that it's hard to block them individually. A mass block option would be ideal but I'm not aware of one being available.
If an emailed message is longer than an SMS, it will likely show up an a MMS
instead. If your messaging app has an option to *not* download the content
of a MMS automatically, a workaround might be to set it that way. You'll still
see the message notification, and you can just delete the message based
on where it's from but the body of the junk won't noise up your messages.
I realize that the notifications themselves might be the most annoying part, but
anything that gets a little more control might help... look around your device
for more call-blocking options too, I *think* some of what you can set in
the dialer app affects messaging too.