Thankfully, there's "nc" to the rescue. nc (or netcat) has a very fine man page that suggests it can do more than telnet does and that it's easily scriptable. I don't know if I care about that, but I do care about this:
$ nc s1.xnnd.com 25
220 happydance.xnnd.com ESMTP Postfix (Ubuntu)
221 2.0.0 Bye
Smells like a good enough replacement for telnet as far as I'm concerned!