How to track read status for individual recipients by adding pixel tracking

Question

I am build an email application with a feature to see read recipients after sending an email. For example: If I sent an email to P1 and cc P2 & P3, then when P1 opens the email, I as a sender should be able to see that P1 read their email.

To achieve this, I am using Individual Tracking Pixels method wherein I add a pixel to the html that I am sending. But the challenge is that, I am not able to send all the recipients unique tracking links since the HTML part of the email is same for everyone and I don't control which email is sent to which recipient (here, P1, P2 & P3).

Answer 1

Include the recipient email/ID as a parameter in the tracking pixel URL

Example: http://example.com/[email protected]

Your tracking server can extract the recipient data from the URL

Answer 2

I would assume here that you do comply with relevant privacy regulations by informing users sufficiently about the tracking practice. It is generally recommended to allow users to opt out of tracking, and to only use tracking for legitimate purposes.

If you do, then you might consider, to implement individual tracking pixels for each recipient (so-called "Spy Pixel"):

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Unique Tracking Links for Recipients: The solution should help in generating unique tracking links or pixels for each recipient, even when the HTML part of the email is identical for all. It should allow the system to identify which recipient (P1, P2, or P3) opened the email individually.

Step 1: Unique Tracking Links for Recipients

1.1 Generating Unique Identifiers

Create unique identifiers for each recipient. Use a hashing algorithm (like hashlib) to generate a unique hash for every recipient using their email address and a secret key.

def generate_unique_identifier(email_address):
    import hashlib
    secret_key = "your_secret_key"
    unique_identifier = hashlib.sha256((email_address + secret_key).encode()).hexdigest()
    return unique_identifier

1.2 Creating Individualized Emails

Instead of sending a single email with all pixels embedded, you need to send individualized emails to each recipient with only their specific tracking pixel embedded in the HTML content of the email.

<!-- Email HTML for P1 -->
<img src="https://yourtrackingserver.com/track/UNIQUE_IDENTIFIER_FOR_P1" width="1" height="1" alt="" />

<!-- Email HTML for P2 -->
<img src="https://yourtrackingserver.com/track/UNIQUE_IDENTIFIER_FOR_P2" width="1" height="1" alt="" />

<!-- Email HTML for P3 -->
<img src="https://yourtrackingserver.com/track/UNIQUE_IDENTIFIER_FOR_P3" width="1" height="1" alt="" />

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Technical Details: The solution should provide step-by-step technical guidance on how to implement the proposed system, including necessary code snippets, configurations, or integrations with existing email protocols or platforms.

Step 2: Technical Details

2.1 Setting Up a Server

Set up a server using a back-end framework such as Flask to handle the tracking. Configure a route to capture GET requests using the unique identifiers.

from flask import Flask, request

app = Flask(__name__)

@app.route('/track/<unique_identifier>', methods=['GET'])
def track(unique_identifier):
    # Log the access to the database
    log_access(unique_identifier)
    return send_pixel_response()

2.2 Logging the Access

Within the tracking route, record each access with its respective unique identifier and the time of access in a database.

import datetime

def log_access(unique_identifier):
    access_time = datetime.datetime.now()
    # Log the access time and the unique identifier to a database
    log_to_database(unique_identifier, access_time)

See for more details "How to log to a Database with Flask" from Matthew Moisen.

2.3 Sending a Transparent Pixel

To maintain a seamless experience for the recipient, the server should return a 1x1 transparent pixel image as a response to the GET request.

from flask import send_file

def send_pixel_response():
    # Return a 1x1 transparent pixel
    return send_file('path/to/transparent_pixel.png', mimetype='image/png')

Answer 3

In short: email as a technology wasn't supposed to support tracking opens. And that's good. The existing pixel-based solutions are a hack and only work since some email clients allow html rendering.

Having this tracking by default on the client level will likely break a lot of privacy laws in different developed countries.

But yes, you have to generate a different tracking id for every user, so the emails will have to be sent separately. That's basically exactly how marketing people do it in mass emails and spam.

To do it as you've described: sending the same email to multiple recipients and seeing who opened them, you'll have to have access to their client. But that's unlikely to happen since no one wants to use a client that spies on them.

The pixel approach will work only if the recipients render html and allow external resources in emails. Which a lot of people have enough sense to rarely do. And certainly never in casual emailing. Even email marketeers can't really use the open rate meaningfully. Too few people allow remote content unless you incentivize them. Like having a special desirable code in an externally loaded image or something akin to that.