README

Overview

The Email Verification App is a Streamlit-based web application designed to validate email addresses using SMTP checks. It provides two modes of operation:

1. Single Verification: Verify a single email address.
2. Batch Verification: Verify multiple email addresses from an uploaded Excel file.

In batch mode, the application displays a progress bar, calculates estimated completion time, and allows for partial results to be saved and downloaded in case of interruptions.

Features

• Single Verification:

  • Input a single email address.
  • Checks the email against default SMTP servers and domain-specific MX records.
  • Displays whether the email is verified or not.

• Batch Verification:

  • Upload an Excel file containing a column named "Email".
  • Specify start and end rows to limit the range of emails to verify.
  • Customize the output file name.
  • Shows real-time progress updates, including elapsed time and estimated completion time.
  • Periodically saves partial results every 10 records processed, enabling partial recovery if the process is interrupted.
  • Offers downloadable Excel files for both verified and unverified emails once processing is complete or interrupted.

How It Works

1. Email Verification Logic:

   • Extracts domain from the email.
   • Retrieves MX records for the domain via DNS lookups.
   • Attempts verification first against default Gmail SMTP servers. If unsuccessful, tries domain-specific MX servers.
   • Verification attempts include handling temporary and timeout errors by retrying after exponential backoff intervals.

2. Batch Processing:

   • Utilizes Python's concurrent.futures.ThreadPoolExecutor for parallel processing of multiple emails.
   • Tracks progress using a progress bar and dynamically updated status text.
   • Saves partial results periodically to prevent data loss.

3. Session State:

   • Uses Streamlit's session state to manage intermediate data (verified/unverified emails), progress indicators, and mode switches.
   • Allows clean restarts and interrupts to the verification process.

Requirements

• Python 3.7+
• Packages:
  • streamlit
  • pandas
  • dns.resolver (from dnspython)
  • openpyxl (for reading/writing Excel files)

Install the required packages with:

pip install streamlit pandas dnspython openpyxl

Running the App

Run the following command in your terminal:

streamlit run app.py

Replace app.py with the filename of the script if different.

Usage

• Select a mode from the radio button: Single Verification or Batch Verification.

• In Single Verification:

  • Enter an email address and click "Check".
  • Results will be displayed on the screen.

• In Batch Verification:

  • Upload an Excel file containing a column named "Email".
  • Specify Start Row and End Row to define the verification range.
  • (Optional) Enter a custom file name prefix.
  • Click "Start Verification" to begin.
  • Monitor the progress bar and status updates.
  • Download the verified and unverified results once done or after an interruption.

Notes

• If the verification process is interrupted or encounters an error, partial results (verified/unverified emails) can be downloaded.
• The app tries to handle temporary SMTP errors by retrying connections.
• Valid emails are marked as "250" status, while invalid or undeliverable emails have associated error codes and messages.