Caution: My disappointing experience with a prominent email validation platform

Other Questions Mailgun
1

I want to share a frustrating experience my company encountered while using an email deliverability service. This serves as both a warning and an account of what we faced.

We relied on this service for email validation, checking deliverability, and monitoring inbox placements, but it wasn’t our primary email service provider or CRM.

The service in question was Mailgun/Sinch. We opted for them in early 2024 due to their attractive pricing compared to our prior provider. Everything seemed fine until we faced a significant issue on Christmas 2024.

On that day, we were hit with over 10 million unexpected email validations in our account, resulting in a substantial overage fee. We thoroughly checked and confirmed that these emails did not come from our forms or internal users. It was quite a shock coming back to work after the holiday break.

Then, in early 2025, history repeated itself. We saw 6 million email validations flood our account again, with the same confirmation that it wasn’t from our systems. They again denied any fault and charged us another fee for the overage.

After that, we decided to return to our original email service provider and ended our contract with Mailgun in June 2025. Then, just the day after our contract concluded in July 2025, I received an email from them claiming we owed over $30,000.

I flagged the email as suspicious and reached out to our account manager but haven’t received a response yet. This only reinforces my suspicion that they experienced security breaches all along.

Ultimately, the takeaway here is that sometimes spending a bit more initially can save you from significant headaches down the line. Be vigilant when selecting these services.

2

Wow, that’s absolutely wild! Getting hit with a massive bill the day after your contract ended shows their true colors. Classic predatory billing tactics. I’d dispute those charges through your bank or credit card company if they processed any payments. Also worth checking if other users have reported similar issues with Mailgun recently - could be part of a bigger pattern.

3

That $30,000 bill after contract termination is a huge red flag. I’ve seen this before - providers trying to squeeze out final payments with bogus charges. The timing’s super suspicious too. They waited until the day after your contract ended because they knew you’d fight it while still under contract. Check your original contract terms, especially termination clauses and validation usage caps. If they keep pushing for payment without proper justification, file a complaint with your state’s business bureau. Those unexplained validation spikes you mentioned? Could be their systems got compromised or misconfigured. That’s not your problem to pay for.

4

The issues you faced with Mailgun are concerning. It’s troubling to see such unexpected spikes in email validations without a reasonable explanation. Effective monitoring and transparency are critical for any service provider, especially when it comes to security and billing. Document all interactions and transactions with them, as this could be vital if disputes arise. If your account manager remains unresponsive, consider alternative methods to reach out. Your experience is a valuable warning for others evaluating similar services.