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 emails sent to a set of contacts hit a 15% bounce rate, those contacts may be quarantined. Industry averages hover closer to 1%, so HubSpot uses a stricter threshold to protect shared IPs.
Quarantining also happens when lists are purchased, scraped, or inherited from messy databases.
If a record looks unverified or spammy, HubSpot removes it from circulation before it can harm your sender reputation.
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 Inherited databases with duplicates, incomplete fields, or outdated information can all trigger flags.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 block these contacts before they drag down deliverability.
How to protect existing contacts
Start by making sure every record in your CRM has a clear legal basis for processing. HubSpot provides a property for this, and keeping it accurate is the best way to prove permission.
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 list from import.” This makes it easier to bulk update properties like legal basis for processing and subscription preferences.
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 Contacts > More Filters > List 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 valid form submission
- Replied directly to a one-on-one email
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.
