email_verification.py

from dns import resolver
import smtplib
import socket
import re

#FIRST CHECK
def check_syntax(email):
    regex = r'^[a-z0-9]+[\._]?[a-z0-9]+[@]\w+[.]\w{2,3}$'
    if(re.search(regex,email)):
        print("Check 1 (Syntax) Passed")
    else:  
        print("Check 1 FAILED! Bad Syntax, Invalid Email!")
        exit()

#SECOND CHECK
def check_dns(email,domain):
    try:
        records = resolver.resolve(domain, 'MX')
        mxRecord = str(records[0].exchange)
        print("Check 2 (DNS -",mxRecord+") Passed")
        return mxRecord
    except:
        print("Check 2 FAILED! The domain",domain,"does not exist, Invalid Email!")
        exit()

#THIRD CHECK
def check_response(email, domain, mxRecord):
    try:
        # Get local server hostname
        host = socket.gethostname()

        # SMTP lib setup (use debug level for full output)
        server = smtplib.SMTP()
        server.set_debuglevel(0)

        # SMTP Conversation
        server.connect(mxRecord)
        server.helo(host)
        server.mail(email)
        code, message = server.rcpt(str(email))
        server.quit()

        # Assume 250 as Success
        if code == 250:
            print("Check 3 (SMTP response) Passed")
            print(email,"is a VALID email address!")
        else:
            print("Check 3 FAILED! The user",email.split("@")[0],"does not exist, Invalid Email!")
    except socket.error as socketerror:
        print("Check 3 HALTED! The domain",domain,", either does not have an SMTP or have restricted access through external scripts")

email = input("Enter your Email id :")
domain = email.split("@")[-1]
check_syntax(email)#CHECK1
mxRecord = check_dns(email,domain)#CHECK2
check_response(email,domain,mxRecord)#CHECK3