How to prevent HubSpot quarantined (blocked) contacts
Protect your sender reputation by managing risky contacts
Email deliverability lives and dies on reputation.
HubSpot protects that reputation by carefully monitoring your contact lists.
If you’re on a shared IP address (which most HubSpot customers are unless they purchase a dedicated one), your sending reputation is tied to every other customer on that IP.
That means a few bad actors can put everyone at risk.
Quarantined contacts are one of the ways HubSpot keeps the pool clean.
More context on quarantined contacts in HubSpot
When HubSpot quarantines a contact, you can no longer send them marketing emails or automated workflow messages.
This usually happens when HubSpot detects suspicious activity or risky patterns. For example, if your marketing emails exceed a 5% hard bounce rate, HubSpot may suspend your sending or quarantine the offending contacts.
While industry averages are closer to 1%, HubSpot sets a strict 5% limit to protect shared IP reputation.
Quarantining also happens when lists are purchased, scraped, or inherited from messy databases.
HubSpot uses historical email data (Global Bounces) to identify and quarantine addresses that have already hard-bounced across three or more other HubSpot accounts.
What causes quarantined contacts
A few common triggers lead to quarantining:
- High bounce rates. Sending to addresses that don’t exist or can’t receive mail
- Non-organic list sources. Uploading purchased or scraped contacts is a direct violation of HubSpot’s acceptable use policy
- Dirty data. Inherited databases with duplicates, incomplete fields, or outdated information can all trigger flags
- Third-party spam. In rare cases, malicious actors may inject contacts to flood inboxes and trip filters
Any of these issues put your account at risk.
HubSpot will move these records to an 'omitted' or 'quarantined' status, automatically excluding them from marketing email eligibility.
How to protect existing contacts
Start by making sure every record in your CRM has a clear legal basis for processing.
HubSpot provides the 'Legal basis for processing contact's data' property for this, which must be enabled in your Privacy & Consent settings.
Look at engagement signals too.
If a contact opens, clicks, or views pages regularly, they’re far less likely to be flagged.
For new records, consider sending a short re-engagement sequence (one email and a follow-up).
If they don’t interact at all, remove them from your marketing lists before HubSpot does it for you.
How to protect future contacts
When importing new lists, always check 'Create a list from this import.' This allows you to immediately run a List Validation check if you have the Marketing Hub Operations tools enabled.
Once the list is created, edit in bulk so every new record has the right subscription status and processing basis. This upfront step saves you from compliance issues later.
After import, navigate to CRM > Segments (or CRM > Lists) to view your new contacts and manage their membership.
From there, you can edit subscriptions for the entire group to align with your marketing permissions.
If you’re cleaning up quarantined contacts, it’s worth also understanding unsubscribes and suppression lists; click on the highlighted text to check it out.
Exceptions to quarantining
Not every contact is at risk.
HubSpot exempts contacts who:
- Have opened or clicked a marketing email
- Opted in through a HubSpot form submission or a confirmed double opt-in
- Replied to a one-on-one email sent from a connected inbox where they were the only recipient.
These interactions prove the address is valid and active, so HubSpot will not quarantine them
Need help?
Managing HubSpot data is hard enough without losing good contacts to quarantines. If your marketing and sales systems are connected (especially through a Salesforce integration) the stakes are even higher.
At RevBlack, we work with mid-market companies that need Salesforce and HubSpot running side by side without deliverability risks or data confusion. We design integrations that keep your lists clean, your reports accurate, and your IP reputation safe.
Need assistance troubleshooting quarantined contacts or preventing them altogether? Reach out.
Still stuck? See HubSpot’s documentation on quarantined contacts.
