Assuming this is for scripting and such, you might take a look at the command-line "mail" command that comes builtin to most Unix-like operating systems. I think the most common implementations are called "mailx" and "nail". With these, there's not even any curses interface, although (like Mutt's default configuration) they rely on a local SMTP server to get the message out. [There may be a way to configure that, but I don't know it.]
Another alternative, again assuming a mostly non-interactive nature, would be to simply write a solution in C or Perl or something. It's not too terribly hard to write a program (especially in a language like Perl) to connect to an external SMTP server and send a message. I wrote a small one in Python that essentially forwards Mutt emails to external SMTP servers. I've also written about a ten-liner SMTP client in Ruby.