For the innovative category of the 2023 ZeroBounce Hackathon.

There is no point in sending an email that a human will never read

Contents

Demo

Preview

Intention

We have built a validation check that validates format and performs a SMTP validation step on the recipient MX. This works well, but it wouldn’t be a good hackathon without pushing the envelope — So we want to take it an extra step and innovate.

B2B sales, particularly in the tech space, frequently works with customers who have a web presence, so why not go another step and validate that the recipient domain has an active website? This further reduces the likelihood of sending email to a parked domain when reverifying old contact lists or as a sanity check on an existing one.

Purpose

To build a scalable and accurate validator to maximize the chances of deliverability to a human.

The team recognizes the methodologies below are not new to the email industry. We decided to not only build a tool that validates emails but also add some additional information for email lookups, checking for an active website, and logo.

Team

Project

Validation Methodology

1. Validate Email format - Start with the basics, is this a valid email address format?

2. Transform Base email format - Transform syntax sugar to simple email.
   1. eg. user+name@domain.com to user@domain.com

3. Validate Domain exists - Dig to validate the domain is valid

4. Validate MX is valid - Does the domain accept email?

   

5. SMTP Verification - Attempt to start a conversation about an email address.
   1. If we are blocked, apply a cooldown on the target IP and email address.

Code and APIs

All APIs used in this demo are internally built.

• Initial draft and much of the early work may be found on Replit.

• I host my own “hackathon framework” (similar to Replit) to help stand up individual services called Serial. This hosts the main code found in the demo.
  • Validation API endpoint - See an example response here
  • Template
  • Form

• SMTP Validation - PHP script on Linode [code]

• Business scraping tools is a web spider I built - Code is available upon request — It’s a separate app I built on Serial.

Blockers

• Some receiving MXs had significant cooldown times between sends, particularly with Cox.net emails. The validated list provided frequently worked once, then would not work and return: 452 4.1.0 <sender> server temporarily unavailable. Refer to Error Codes section at https://www.cox.com/residential/support/email-error-codes.html for more information. AUP#CXMXRT
  • Intelligent management of proxy IPs rotating around this cooldown for a scalable long-term fix. Long shot, but it may be worth a conversation with the Cox business team for partnership.

• Cloudflare-hosted MX rejected requests that do not have a reverse IP lookup.

Future work

Hackathons rarely grow beyond their initial scope, however, if this project were to continue development, I’d add the following:

• Multiple line input

• CSV Import / Export

• Intelligent management of caching and validating against the same MX for a domain.

• Scaling to more requests

• IP Proxy rotation