Php – SMTP protocol issue with Zend_Mail

You are facing 3 problems:

First, you are not reading entire response of EHLO command.

This command has multi-line response:

250-mx.google.com at your service, [203.99.179.10] 
250-SIZE 35882577 
250-8BITMIME 
250-STARTTLS 
250 ENHANCEDSTATUSCODES

Note the space after last 250 code - it means that this is the last response line.

Second: EHLO should be the first command you send.

Third: Gmail does not allow to log-in without using SSL, either implicit (on 465 port) or explicit (STARTTLS command)

You can ssl wrap a connected socket. This will give you the idea:

import ssl
import base64
from socket import *


cc = socket(AF_INET, SOCK_STREAM)
cc.connect(("smtp.gmail.com", 587))
# cc.read(..)

cc.send('helo tester.com\r\n')
cc.send('starttls\r\n')
# cc.read(..) If the server responds ok to starttls
#             tls negotiation needs to happen and all
#             communication is then over the SSL socket 

scc = ssl.wrap_socket(cc, ssl_version=ssl.PROTOCOL_SSLv23)
scc.send('auth login\r\n')
# scc.read(..)

scc.send(base64.b64encode('username')+'\r\n')
scc.send(base64.b64encode('password')+'\r\n')

# css.send(
#  mail from:
#  rcpt to:
#  data
#  etc

look at the AUTH LOGIN section of this page for info about the username/password encoding: http://www.samlogic.net/articles/smtp-commands-reference-auth.htm

After that the AUTH LOGIN command has been sent to the server, the server asks for username and password by sending BASE64 encoded text (questions) to the client. “VXNlcm5hbWU6” is the BASE64 encoded text for the word "Username" and “UGFzc3dvcmQ6” is the BASE64 encoded text for the word "Password" in the example above. The client sends username and password also using BASE64 encoding. "adlxdkej", in the example above, is a BASE64 encoded username and "lkujsefxlj" is a BASE64 encoded password.