MX Record Resolver for Email Provider

mx_resolver.py

## MX Record Resolver for Email Provider
# 
# This script takes a CSV file with a column of email addresses and adds a column
# with the email provider (e.g. Google, Microsoft, etc.) based on the MX record
# of the email address domain.
#
# The MX record is the DNS record that specifies the mail server responsible for
# accepting email messages on behalf of a domain name. The MX record is used to
# route email messages to the correct mail server.
#
# We can use the MX record to guess the email provider of an email address.
#
# The script uses the dnspython library to resolve the MX record of the domain.
# The script will prompt the user for the CSV file name, the name of the email
# column, and the desired output file name. The script will then save the
# processed data to a new CSV file.
#
# Requirements:
# - Python 3
# - dnspython library (pip install dnspython)
# - pandas library (pip install pandas)
#
# Usage: python mx_resolver.py
#
# Author: Lauri Jutila (@ljuti)
# URL: https://neuraljets.com
# License: MIT

import os
import pandas as pd
import dns.resolver

def get_email_provider(mx_record):
    if 'google' in mx_record or 'googlemail' in mx_record:
        return 'Google (Gmail)'
    elif 'outlook.com' in mx_record or 'office365.com' in mx_record or 'mail.protection.outlook.com' in mx_record:
        return 'Microsoft (Outlook/O365)'
    else:
        return 'Other'

def file_exists(filename):
    return os.path.isfile(filename)

def get_valid_filename(prompt):
    while True:
        filename = input(prompt)
        if file_exists(filename):
            return filename
        else:
            print("File not found. Please try again.")

def get_valid_column(df, prompt):
    while True:
        column_name = input(prompt)
        if column_name in df.columns:
            return column_name
        else:
            print("Column not found. Please try again.")

def process_csv(input_file, email_column, output_file):
    # Read CSV
    df = pd.read_csv(input_file)

    # Extract domain and find email provider
    df['domain'] = df[email_column].apply(lambda x: x.split('@')[-1])
    df['email_provider'] = ''

    for index, row in df.iterrows():
        try:
            mx_records = dns.resolver.resolve(row['domain'], 'MX')
            mx_record = str(mx_records[0].exchange).lower()
            df.at[index, 'email_provider'] = get_email_provider(mx_record)
        except Exception as e:
            df.at[index, 'email_provider'] = 'Unknown'

    # Save to new CSV
    df.to_csv(output_file, index=False)
    print(f"Processed data saved to {output_file}")

# User input for file names and column name
input_file = get_valid_filename("Enter the filename of the CSV: ")
df = pd.read_csv(input_file)
email_column = get_valid_column(df, "Enter the name of the email column: ")
output_file = input("Enter the desired output file name: ")

# Process the CSV
process_csv(input_file, email_column, output_file)