Haskell - Connection and smtp

Question

Following this : Using tls-extra for simple smtp, I am trying to write a script to send a mail via gmail(the gmail bit is not mandatory)
I have written this :

{-# LANGUAGE OverloadedStrings #-}

import Network.Connection
import Data.Monoid                             ((<>))
import qualified Crypto.Random.AESCtr   as RNG (makeSystem)
import Data.ByteString                         (ByteString)
import qualified Data.ByteString.Char8  as BC  (isPrefixOf)
import qualified Data.ByteString.UTF8   as BU  (fromString,toString)
import qualified Data.ByteString.Base64 as BE  (encode)
import Data.Text                               (Text, unpack)

gmail :: (Text, Int)
gmail = ("smtp.gmail.com", 587)

readHeader :: Connection -> ByteString -> IO ()
readHeader con code = do
    hea <- connectionGetLine 1024 con
    putStrLn $ show hea
    if code `BC.isPrefixOf` hea
    then return ()
    else readHeader con code

emailT :: (Text, Int) -> (Text, Text) -> Text -> Text -> Text -> IO ()
emailT provider auth from to email = do
    ctx <- initConnectionContext
    con <- connectTo ctx $
        ConnectionParams
        { connectionHostname  = unpack $ fst provider
        , connectionPort      = 587
        , connectionUseSecure = Nothing
        , connectionUseSocks  = Nothing
        }
    g <- RNG.makeSystem
    connectionGetLine 1024 con >>= putStrLn . show
    connectionPut con "EHLO\n"
    readHeader con "250-STARTTLS"
    connectionPut con "STARTTLS\n"
    readHeader con "220"
    connectionSetSecure ctx con $ TLSSettingsSimple False False False
    connectionPut con "EHLO\n"
    readHeader con "250"
    connectionPut con "AUTH LOGIN\n"
    readHeader con "334 "
    connectionPut con $ BE.encode $ BU.fromString $ unpack $ fst auth
    readHeader con "334"
    connectionPut con $ BE.encode $ BU.fromString $ unpack $ snd auth
    readHeader con "235"
    connectionPut con $ BU.fromString $ unpack ("MAIL FROM:<"<> from <>">")
    readHeader con "250"
    connectionPut con $ BU.fromString $ unpack ("RCPT TO:<"<> to <>">")
    readHeader con "250"
    connectionPut con "DATA\n"
    readHeader con "354"
    connectionPut con $ BU.fromString $ unpack email
    connectionPut con "\r\n."
    readHeader con "250"
    connectionPut con "QUIT\n"
    readHeader con "221"
    connectionClose con

main = emailT gmail ("mygmailuser", "mygmaipass") "test" "test" "test"

The discussion goes well until the AUTH LOGIN part. At first I though I was misreading some headers but I am not so sure now. I believe the problem has more to do with my handling of smtp that my code here.