Original version tried to import SSLFakeFile and SSLFakeSocket which aren't present in imaplib 2.58 so I've added them manually (after simply googling them)

tlsimap.py

""" Python IMAP with TLS/SSL support """
##
## Author: Alexander Brill <alex@brill.no>
## Copyright (C) 2004 Alexander Brill
##
## This program is free software; you can redistribute it and/or
## modify it under the terms of the GNU General Public License
## as published by the Free Software Foundation; either version 2
## of the License, or (at your option) any later version.
##
## This program is distributed in the hope that it will be useful,
## but WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with this program; if not, write to the Free Software
## Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
##

"""USAGE:
import imaptls
imap = imaptls.IMAP4('hostname')
imap.starttls(keyfile=None, certfile=None)

# create a simple function for our PLAIN login
def sendAuth(response):
    return "user\0auth\0password"

typ, data = imap.authenticate("PLAIN", sendAuth)
"""


import imaplib, socket

class SSLFakeSocket:
    """A fake socket object that really wraps a SSLObject.

    It only supports what is needed in smtplib.
    """
    def __init__(self, realsock, sslobj):
        self.realsock = realsock
        self.sslobj = sslobj

    def send(self, str):
        self.sslobj.write(str)
        return len(str)

    sendall = send

    def close(self):
        self.realsock.close()

    def shutdown(self, *args, **kwargs):
        pass
        
        
class SSLFakeFile:
    """A fake file like object that really wraps a SSLObject.

    It only supports what is needed in smtplib.
    """
    def __init__(self, sslobj):
        self.sslobj = sslobj

    def readline(self):
        str = ""
        chr = None
        while chr != "\n":
            chr = self.sslobj.read(1)
            if not chr:
                break
            str += chr
        return str

    def read(self, size):
        tmp = ""
        prevLen = -1
        tmpLen = 0
        while tmpLen != prevLen and tmpLen != size:
            prevLen = tmpLen
            tmp += self.sslobj.read(size - prevLen)
            tmpLen = len(tmp) 
        return tmp

    def close(self):
        pass 

Commands = {
    'STARTTLS': ('NONAUTH')
    }
imaplib.Commands.update(Commands)


class IMAP4(imaplib.IMAP4):
    
    def starttls(self, keyfile = None, certfile = None):
	name = "STARTTLS"
	typ, dat = self._simple_command(name)
	if typ != 'OK':
	    raise self.error(dat[-1])
	sslobj = socket.ssl(self.sock, keyfile, certfile)
	self.sock = SSLFakeSocket(self.sock, sslobj)
	self.file = SSLFakeFile(sslobj)
	
	cap = 'CAPABILITY'
        self._simple_command(cap)
        if not cap in self.untagged_responses:
            raise self.error('no CAPABILITY response from server')
        self.capabilities = tuple(self.untagged_responses[cap][-1].upper().split())

Hi,

I'm digging this.....

In python3 socket.ssl doesnt exist. DId you have any idea to port that ?

Thanks

Woa this is old. I had to look what this was. Still not sure for which project I used this. But... Did you try

print(dir(socket))

Maybe the .ssl is private now?

Well I checked and no :/

@nathan30 - imaplib in Python3 has its own starttls() function. Wouldn't you want to use that instead if using Python 3?
https://docs.python.org/3.5/library/imaplib.html#imaplib.IMAP4.starttls