I'm actually aware that I can get the address which the email is sent from, but I wonder if I can get the user name of de sender too. I searched on the email module documentation but I didn't find anything about it.
Short answer: no, you can't.
Username of the sender remains between the SMTP server and the sender; it's never included in the data sent outside, unless the sender explicitly typed it into the email text. Note that there can be several hops between the originating SMTP server and the receiving SMTP server.
IMAP servers are used to access received mail; they have no idea how it was sent.
Is there anyway I can get user name from a MIME object in python?