HubSpot Contact Search API & hs_additional_emails: Undocumented Behavior & E-commerce Risks

Hey ESHOPMAN community! As experts in connecting your ecommerce store creator with the power of HubSpot, we’re always digging into the nitty-gritty details that can make or break your operations. Recently, a fascinating discussion popped up in the HubSpot Community that sheds light on a subtle but significant behavior within the HubSpot Contact Search API. It’s the kind of insight that can save RevOps teams and marketers a lot of headaches, especially when managing customer data across various systems.

The Curious Case of HubSpot’s Email Search

The original poster in the community thread brought up an interesting discovery: when using the POST /crm/v3/objects/contacts/search endpoint with an email EQ (equals) filter, they found that the search wasn't just matching the primary email address on a contact record. Instead, it was also returning contacts where the queried email was stored in the hs_additional_emails field.

Imagine this scenario:

You have a contact, Jane Smith, with jane@primarydomain.com as her primary email.
But Jane also has jane@secondarydomain.com listed in her hs_additional_emails field (perhaps from a previous merge or an old interaction).
If you search for jane@secondarydomain.com using the API, HubSpot returns Jane Smith’s contact record, even though jane@primarydomain.com is her main identifier.

Here’s the sample request that demonstrated this behavior:

POST https://api.hubapi.com/crm/v3/objects/contacts/search
{
  "filterGroups": [
    {
      "filters": [
        {
          "propertyName": "email",
          "operator": "EQ",
          "value": "user@secondarydomain.com"
        }
      ]
    }
  ],
  "properties": ["email", "firstname", "lastname", "hs_additional_emails"]
}

The contact returned had user@secondarydomain.com in hs_additional_emails, with a completely different address as the primary email. This is crucial for anyone building integrations or relying on precise email lookups.

HubSpot Support’s Stance: It Works, But Don’t Rely On It (Yet)

The original poster wisely reached out to HubSpot Support for clarification. Their response was illuminating:

The observed behavior (email EQ matching hs_additional_emails) is consistent with current HubSpot functionality.
However, it’s not explicitly documented as part of the Search API contract.
HubSpot Support does not recommend relying on it as guaranteed long-term behavior.
They acknowledged this as a documentation gap and have submitted internal feedback.

This is a classic "works today, but might not tomorrow" situation. For teams building custom integrations or managing complex data flows, this uncertainty is a big deal.

Why This Behavior Might Be Necessary

A community member weighed in, suggesting that this behavior, while perhaps unexpected, is "totally necessary" when considering how HubSpot handles duplicate email addresses. If searching for an email failed to find it in hs_additional_emails, your next step might be to try and create a new contact. This would then fail when HubSpot's uniqueness test kicks in, as that email is already associated with an existing contact. It’s a mechanism that likely helps prevent the creation of true duplicate contacts, even if the email isn't the primary one.

The hs_additional_emails field itself can grow over time, often populated intentionally or accidentally through contact merges. This means the set of emails that resolve to a given contact can expand without direct API action, which has significant implications for integrations that assume a strict 1:1 match on the primary email.

The Real-World Impact: Portal Access and External SSO

While preventing duplicates is good, the original poster highlighted a more concerning side effect: potential security and access control issues, especially for HubSpot portals and integrations with external Single Sign-On (SSO) systems. They observed that HubSpot portal access appears to work the same way – a user can access content using an address that matches their hs_additional_emails, depending on portal configuration.

The critical scenario they outlined involved merged contacts:

"Unfortunately our Contacts can contain both work emails and personal emails, and if a Sales Person merges a Work Contact and a Personal Contact, that Contact can access a Portal with their personal email that should only be accessible to someone with their work email access."

This is a huge red flag for RevOps and security-conscious marketers. If you’re using an external SSO service (common for a comprehensive customer ecosystem including support, community, and training sites), and that SSO system is tied to HubSpot contacts, then any email (primary or additional) associated with a contact could potentially grant access. The original poster successfully demonstrated this by creating two distinct users in their external SSO, linking a secondary email to a HubSpot contact, and then logging into a HubSpot portal with that secondary email.

Think about it: if a former employee's personal email was accidentally merged into their work contact record, and that personal email is still active in your external SSO, they might retain access to sensitive company resources via your HubSpot portal, even after leaving the company. This could be a nightmare for compliance and data security.

Mitigating the Risk: What Can You Do?

The community discussion explored some mitigation strategies:

Membership Lists: A community member suggested using membership lists for portal access. The idea is that only contacts explicitly added to a list (presumably via their primary email) would be invited and receive password communications. However, the original poster's SSO test showed that if a secondary email is already associated with a contact on a membership list, and that email is valid in SSO, access can still be gained.
Manual Cleanup: Another suggestion was to manually delete secondary email addresses from any contact record in the UI to fix a perceived "leak." While possible, this is hardly a scalable or proactive solution for large databases or frequent merges.
Strict SSO Configuration: For those using external SSO, it's paramount to understand how your SSO provider validates users against HubSpot data. Can it be configured to only recognize the primary email, or specific domains? This might require a deeper dive into your SSO provider's capabilities and integration with HubSpot.
API Vigilance: If you're building custom integrations, be aware that relying on the email EQ filter to only match the primary email is risky. You might need to implement additional logic to explicitly check the email property versus hs_additional_emails if precise matching is critical for your application.

ESHOPMAN Team Comment

This discussion highlights a critical area where undocumented HubSpot behavior can have significant, unintended consequences for e-commerce businesses. We believe that while HubSpot's current API behavior might prevent duplicate contact creation, the lack of explicit documentation and the potential for unauthorized portal access via hs_additional_emails, especially with external SSO, is a serious concern. ESHOPMAN recommends a proactive approach: always assume hs_additional_emails can grant access if linked to an SSO, and design your access control and integration logic with this in mind, rather than waiting for HubSpot to formalize or change the behavior.

The Takeaway for Your E-commerce Operations

For RevOps leaders and marketers running an online store, managing customer data accurately and securely is non-negotiable. Whether you're using HubSpot as your primary CRM, leveraging it as an ecommerce store creator backend, or integrating it with other platforms like Salesforce or Magento CRM, understanding these nuances is vital. This community thread is a fantastic example of why staying engaged with the HubSpot developer community and regularly testing your integrations is so important. Don't assume; verify. And if you find undocumented behavior, share it – you might just help prevent a major security or data integrity issue for someone else!