Instead of SMTP which is used for sending emails, you should use either POP3 or IMAP (the latter is preferable). Example of using SMTP (the code is not mine, see the url below for more info):
import imaplib
mail = imaplib.IMAP4_SSL('imap.gmail.com')
mail.login('myusername@gmail.com', 'mypassword')
mail.list()
# Out: list of "folders" aka labels in gmail.
mail.select("inbox") # connect to inbox.
result, data = mail.search(None, "ALL")
ids = data[0] # data is a list.
id_list = ids.split() # ids is a space separated string
latest_email_id = id_list[-1] # get the latest
result, data = mail.fetch(latest_email_id, "(RFC822)") # fetch the email body (RFC822) for the given ID
raw_email = data[0][1] # here's the body, which is raw text of the whole email
# including headers and alternate payloads
Shamelessly stolen from here