No, Android does not provide a way to send an email without opening a client. Why don't you want to use JavaMail?
Another way to do this is to use java.net.Socketto connect directly to the SMTP server. Doing it yourself is a lot easier than it sounds, because the protocol is pretty simple and even human readable.
This page shows an example SMTP session for sending a regular text message:
http://www.smtp2go.com/articles/smtp-protocol.html
Barry