Here's the answer, courtesy of the FAQ at python.org, located here

On Unix, it's very simple, using sendmail. The location of the sendmail program varies between systems; sometimes it is /usr/lib/sendmail, sometime /usr/sbin/sendmail. The sendmail manual page will help you out. Here's some sample code:

  SENDMAIL = "/usr/sbin/sendmail" # sendmail location
  import os
  p = os.popen("%s -t" % SENDMAIL, "w")
  p.write("To: cary@ratatosk.org\n")
  p.write("Subject: test\n")
  p.write("\n") # blank line separating headers from body
  p.write("Some text\n")
  p.write("some more text\n")
  sts = p.close()
  if sts != 0:
      print "Sendmail exit status", sts

On non-Unix systems (and on Unix systems too, of course!), you can use SMTP to send mail to a nearby mail server. A library for SMTP (smtplib.py) is included in Python 1.5.1; in 1.5.2 it will be documented and extended. Here's a very simple interactive mail sender that uses it:

    import sys, smtplib

    fromaddr = raw_input("From: ")
    toaddrs  = string.splitfields(raw_input("To: "), ',')
    print "Enter message, end with ^D:"
    msg = ''
    while 1:
        line = sys.stdin.readline()
        if not line:
            break
        msg = msg + line

    # The actual mail send
    server = smtplib.SMTP('localhost')
    server.sendmail(fromaddr, toaddrs, msg)
    server.quit()

This method will work on any host that supports an SMTP listener; otherwise, you will have to ask the user for a host.