Why from en to two times with sending email

[Cecil Westerhof]

I want to change an old Bash script to Python. When I look at:
    https://docs.python.org/2/library/email-examples.html

Then from and to have to be used two times? Why is that?

-- 
Cecil Westerhof
Senior Software Engineer
LinkedIn: http://www.linkedin.com/in/cecilwesterhof