Welcome to Day 8 of 12 Days of DigitalOcean! Yesterday, you deployed a Flask app on DigitalOcean to build an Email-Based Receipt Processor. This application will let you send receipts to an email address and automatically process them.

Today, you will set up Postmark to handle incoming emails. Postmark receives emails, transforms them into JSON data, and sends it to your app, eliminating the need for you to manage email servers or decode raw email formats.

By the end of this tutorial, emails sent to a dedicated address will be automatically forwarded to your Flask app, allowing you to log, store, or analyze them. Let’s get started!

How It Works

Here’s how the integration operates:

1. A user sends an email (e.g., a receipt) to a Postmark-provided address.
2. Postmark receives the email and processes its content into JSON.
3. This structured data is then sent to your Flask app hosted on DigitalOcean using a webhook URL.
4. Your app processes the data, extracting essential information such as the sender, subject, and body.

Postmark handles the email parsing, enabling your app to focus on utilizing the data, whether that’s storing it in a database, cleaning it, or preparing it for analysis.

Step-by-Step Guide

You’ll begin by updating the Flask app to receive incoming emails, followed by configuring Postmark to send email data to your app.

Step 1 – Update Your Flask App

Your application needs a route to receive email data from Postmark.

1. Open your app.py file and add the following code:

   from flask import Flask, request, jsonifyapp = Flask(__name__)@app.route('/inbound', methods=['POST'])def inbound():    email_data = request.get_json()    subject = email_data.get('Subject', 'No subject')    from_email = email_data.get('FromFull', {}).get('Email', 'Unknown sender')    body = email_data.get('TextBody', '')    print(f"Received email from {from_email} with subject: {subject}")    print(f"Body: {body}")    return jsonify({"status": "success"}), 200

   This code sets up a new /inbound route that listens for POST requests from Postmark, extracts key details from the JSON payload, and logs them.

2. Save the changes to app.py.

3. Commit and push the changes to GitHub to redeploy the app on DigitalOcean:

   git add app.pygit commit -m "Add inbound route for Postmark emails"git push origin main

   Your app is now ready to receive email data from Postmark. Check the DigitalOcean App Platform dashboard to ensure it’s live and grab the public URL, as Postmark will send email data to this URL.

Quick Tip: For local testing, consider using Ngrok to expose your Flask app to the internet temporarily.

Step 2 – Set Up Postmark

Postmark will manage the parsing of emails and forwarding of structured data to your app.

1. Log In to Postmark:

   • If you don’t have an account, sign up for free.

2. Create a Server:

   • Go to the Servers tab and click Create Server. Name the server something like "Receipt Processor".

3. Use the Default Inbound Stream:

   • Access the Default Inbound Stream to utilize its email processing feature and note the provided email address for testing.

Step 3 – Connect Postmark to Your App

You need to configure the webhook URL in Postmark so that it can send email data to your Flask app.

1. Set Your Webhook URL in Postmark:
   • Paste your DigitalOcean app URL in the Default Inbound Stream settings and append /inbound to the end.

Quick Tip: If you switch from testing with Ngrok to a live app URL, return to this field in Postmark settings and update the webhook URL.

Step 4: Test the Setup

Now, it’s time to verify if everything is functioning properly.

1. Send a Test Email:

   • Use the Postmark-provided email address to send a test email.

2. Check Postmark Activity:

   • Verify that the email was received and forwarded correctly by checking the Activity tab in your Postmark dashboard.

3. Verify Your Runtime Logs:

   • Go to DigitalOcean App Platform dashboard, select your app, and check the logs to confirm the email details are logged as expected.

Troubleshooting

If any issues arise, check the following:

1. Ensure your /inbound route is properly set up and your Flask app is running.
2. Verify that the webhook URL in Postmark is correct and includes /inbound.
3. Double-check the email address you’re sending to; it should match the one from Postmark’s default inbound stream.
4. Review Postmark’s Activity Logs and DigitalOcean’s Runtime Logs to diagnose any problems.

Wrapping Up

You successfully added an inbound route to your Flask app to handle emails from Postmark, configured Postmark’s settings, and tested the setup. Your Email-Based Receipt Processor is now equipped to receive and process emails automatically! In the next tutorial, you’ll learn how to enhance this data with AI tools to extract and organize receipt details.

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