This script test the overall process of logging into an email account, going to a specific folder, looking for emails from a specific sender, and extracting desired information from those email messages.

extract_email.py

#!/usr/bin/env python

"""
This script test the overall process of logging into an email account,
going to a specific folder, looking for emails from a specific sender,
and extracting desired information from those email messages.

Sources and Inspirations:
    Extract emails from Gmail with Python via IMAP - http://www.voidynullness.net/blog/2013/07/25/gmail-email-with-python-via-imap/    # NOQA
"""

import re           # regular expression operations
import sys          # operating system specific functions
import email        # email handling and generator package
import imaplib      # connect with IMAP4 protocol client
import getpass      # get user password
import datetime     # manipulation of dates and times

# identify your target email server, emailbox, email message source, and folder
# these are the only messages to be processed and all others skipped
IMAP_SERVER = "imap.gmail.com"
EMAIL_FOLDER = "INBOX"
EMAIL_SOURCE = "WaterReporting@leesburgva.gov"
EMAIL_ACCOUNT = "waterusage@gmail.com"

# this is where a copy of your target emails will be dumped for debugging
OUTPUT_DIRECTORY = "/tmp/email_dump"


# dump the whole email message into a file for debugging
def dump_message(num, data):
    print "\n\nWriting message", num, "to debug directory"

    # open the file where the message is to be dumped
    try:
        f = open('%s/%s.eml' % (OUTPUT_DIRECTORY, num), 'wb')
    except (OSError, IOError) as e:
        print "ERROR: Problem with debug dumping directory", e
        sys.exit(1)

    # write the message into the file
    f.write(data[0][1])
    f.close()


def parse_message(num, data):
    # get the whole message in the form of a string
    msg = email.message_from_string(data[0][1])

    # parse the message's sender, receiver, and content type
    str1 = re.sub('[<>]', '', msg['From'])
    str2 = re.sub('[<>]', '', msg['Delivered-To'])
    if str1 == EMAIL_SOURCE:
        print "Sender:", str1
        print "Receiver:", str2
        print "Content Type:", msg['Content-Type']
    else:
        print "This is not a target message"
        return 0

    # parse out the message's subject and date
    print 'Message %s Subject: %s' % (num, msg['Subject'])
    print 'Raw Date:', msg['Date']

    # reformat date to make it more user friendly
    date_tuple = email.utils.parsedate_tz(msg['Date'])
    if date_tuple:
        local_date = datetime.datetime.fromtimestamp(
            email.utils.mktime_tz(date_tuple))
        print "Day, Date, Time:", \
            local_date.strftime("%a, %d %b %Y, %H:%M:%S")

    # parse out the message's body (assumes the message is not multi-part)
    print "multipart = ", msg.is_multipart()
    if msg.is_multipart():
        print "ERROR: Payload is multipart and can't be processed."
        print "Message Body:", msg.get_payload()
        return 1
    else:
        print "Message Body:", msg.get_payload()
        return 0


def process_mailbox(M):
    # get the message sequence number so you can loop over all the messages
    rv, data = M.search(None, "ALL")
    if rv != 'OK':
        print "No messages found in mailbox!\n"
        return 0

    # fetch the raw message contents for each of the messages
    for num in data[0].split():
        rv, data = M.fetch(num, '(RFC822)')
        if rv != 'OK':
            print "ERROR: Error getting message. error code = ", num
            return 1

        # dump the mail message to a directory
        dump_message(num, data)

        # parse the email message
        rtn = parse_message(num, data)

    return rtn


def list_folders(M):
    rv, folders = M.list()

    if rv == 'OK':
        print EMAIL_ACCOUNT, "Folders are:"
        print folders, "\n"
        return 0
    else:
        print "ERROR: Unable to get list of mailbox folders ", rv
        return 1


def main():
    # get the password from the user
    PASSWORD = getpass.getpass()

    # create an IMAP4 instance (of the SSL variant for security)
    # and connected to the Gmail server at imap.gmail.com
    mailbox = imaplib.IMAP4_SSL(IMAP_SERVER, 993)

    # attempt to login, and if the login fails, raise and exception
    try:
        rv, data = mailbox.login(EMAIL_ACCOUNT, PASSWORD)
    except imaplib.IMAP4.error:
        print "ERROR: LOGIN FAILED!!!"
        sys.exit(1)
    print rv, data, "\n"

    # get a list of the folders associated with the mailbox
    if list_folders(mailbox):
        sys.exit(1)

    # open the mailbox folder you are interested in and process it
    rv, data = mailbox.select(EMAIL_FOLDER)
    if rv == 'OK':
        print "Processing mailbox folder", EMAIL_FOLDER, "..."
        rtn = process_mailbox(mailbox)
        mailbox.close()
        sys.exit(rtn)
    else:
        print "ERROR: Unable to open mailbox ", rv
        mailbox.logout()
        sys.exit(1)


if __name__ == "__main__":
    main()