Email validation fails for some odd reason

Service Hub Tickets & Conversations
1

Hello,

we have a really odd issue. We don’t use HubSpot ourselves, but my colleague cannot register/sign up on sites using HubSpot because her email address is market as “invalid”. Her address is: i.rosiere@sicher-im-netz.de

  • Yes, we made sure there is no typo or empty space or other incorrect character in the field.
  • The domain @sicher-im-netz.de cannot be the cause of the issue, because others with the same domain can register.
  • The dot cannot be the issue either, all of the others have the same structure.
  • If I change the i to another letter at the beginning, it works.
  • If I remove the dot, it works.

It seems the validation mechanic used by HubSpot is being weird for no apparent reason.

Any ideas?

2

Hi @MMeingast,

You’re right to call this an odd issue, and you’re not the first to bump into this with HubSpot’s form validation layer.

The issue is not your domain, nor the dot structure, nor a typo. Instead, HubSpot may be silently rejecting this specific email because of backend blocklists or custom validation rules that are not user-visible.

Here are the most likely causes, with the help of generative AI:

Email address matches a system-wide suppression list

HubSpot maintains an internal global suppression/blocklist of email addresses known for:

  • High bounce rates,
  • Spam complaints,
  • Abuse reports (e.g. from previous form submissions).

If the email i.rosiere@sicher-im-netz.de had ever been marked as spam, bounced, or opted out on any HubSpot-powered form globally — that exact email may be blocked from form use across the HubSpot network.

Test: Try using a different form from a totally different company’s HubSpot site. If it fails there too — it’s on HubSpot’s global suppression list.

Custom JavaScript or Regex Validation on the Form

Some HubSpot customers inject custom validation scripts (especially with embedded forms). These scripts might inadvertently or intentionally block:

  • Short usernames like i.rosiere
  • Certain pattern matches
  • First-letter initials followed by dots

Test: Look at the console (DevTools → Console tab) while submitting the form. Any RegExp or JS error? That may hint at local form rules.

Connected Integrations (like Clearbit, Sift, Kickbox, etc.)

Some HubSpot users connect their forms to email enrichment or verification services. These services run reputation checks and can reject an email even if it’s technically valid.

Test: If the company is using enhanced verification, have your colleague try signing up from a different IP or browser with privacy features turned off (sometimes fingerprinting plays a role).

So unfortunately, this is hard to troubleshoot if you cannot access the page configuration yourself.

An easy way around this could be an email aliasing tool. Personally, I use https://addy.io/ – it’s another layer in front of the actual email address (which is great for privacy reasons and spam management in general) and would be a way to bypass whatever filter is kicking in without having to investigate further.

Best regards!