How to Check a List Against Your HubSpot Database (Before You Accidentally Email Your Own Contacts)
You’ve got a shiny new list.
A campaign ready to roll.
And a quiet fear in the back of your mind:
“Wait… do we already have these people in HubSpot?”
Because nothing kills a launch faster than:
emailing customers who already bought
pitching prospects who are mid-deal
or blasting someone who unsubscribed three years ago and still remembers
Good news: suppressing existing contacts is way easier than it sounds—if you do it the right way.
Let’s walk through the cleanest, least-chaotic way to check a list against your HubSpot database before you send.
The Use Case (AKA: Why This Matters)
This usually comes up when:
You’re sending to a purchased or partner list
You’re running paid media + email together
You’re onboarding a new audience but want net-new leads only
You’re trying not to annoy your existing customers (10/10 goal)
Bottom line:
You want to email new people—not the ones already living comfortably inside your CRM.
The Golden Rule: Never “Guess” Who’s New
Manually eyeballing a spreadsheet = chaos.
Spot-checking emails = false confidence.
Instead, you want HubSpot to tell you who already exists.
Option 1: Import the List (Safely) and Let HubSpot Do the Work
This is the most reliable method—and the one we recommend 99% of the time.
Step 1: Prep Your List
Make sure your file includes:
Email address (non-negotiable)
Any other fields you care about (company, name, etc.)
Save it as a CSV.
Step 2: Import → “Update Existing Contacts Only”
When importing into HubSpot:
Choose Import contacts
Upload your file
Select “Update existing contacts only”
What this does:
HubSpot scans your database
Matches records by email
Updates only contacts that already exist
Ignores net-new emails completely
No accidental adds. No surprises.
Step 3: Create a Smart List from the Import
After the import:
HubSpot automatically creates a list of matched contacts
This is now your suppression list
Anyone not in that list?
👉🏼 They’re net new.
Option 2: Use Lists to Suppress Before Sending
If you’re already planning an email campaign:
Create a static list from your imported file
Create a smart list of “All Contacts” (or a relevant subset)
Suppress the smart list in your send
This is especially useful when:
You’re sending from another platform
You want a reusable suppression list
You’re coordinating email + ads + lifecycle stages
Option 3: Check via Ads (Bonus Move)
If this list is also being used for paid media:
Upload it as a custom audience
Suppress your HubSpot synced lists (customers, leads, etc.)
This keeps your messaging clean across channels—and avoids the “why am I seeing this?” Slack messages.
Common Mistakes to Avoid (Learn From Others)
❌ Importing as “create new contacts”
❌ Emailing before checking lifecycle stage
❌ Forgetting about unsubscribed contacts
❌ Suppressing after the send (pain)
If you’re unsure, default to more suppression, not less.
The TL;DR
If you want to send to a list without hitting existing contacts:
Import the list as “update existing contacts only”
Use the resulting list as your suppression
Let HubSpot do the matching—don’t play detective
Clean data = better deliverability, happier customers, fewer “oops” moments.
If you want help setting this up—or building a repeatable process so your team never has to think about it again—Ritner Digital’s got you.
Because the best campaigns are the ones that don’t annoy people. 😉
FAQs
Will this create new contacts in HubSpot?
Not if you do it correctly.
If you import the list using “Update existing contacts only,” HubSpot will only match and update contacts already in your database. Net-new emails won’t be added.
What does HubSpot use to match contacts?
Email address.
If the email matches an existing contact, HubSpot counts it as the same person. No email = no match.
What happens to contacts that aren’t already in HubSpot?
They’re ignored during the import.
Which is exactly what you want when you’re trying to identify who to suppress.
Can I use this list to suppress emails in HubSpot?
Yes.
After the import, HubSpot automatically creates a list of matched contacts. That list can be used as a suppression list for any email send.
Should I use a static list or an active (smart) list?
Static list: Best for one-time sends or partner campaigns
Active list: Better if you’ll reuse the suppression logic over time
When in doubt, static is safer.
What about unsubscribed or bounced contacts?
They’re already suppressed by HubSpot automatically.
Still, it’s smart to keep them out of external sends too—future-you will be grateful.
Can I check a list without importing it at all?
Not reliably.
HubSpot needs the data inside the system to match emails correctly. Importing with the right settings is the cleanest option.
Does this work for huge lists?
Yes—though large imports can take time to process.
Pro tip: run the import before launch day so you’re not watching a progress bar instead of shipping.
Can I use the same approach for paid ads?
Absolutely.
Upload the list to your ad platform and suppress your HubSpot-synced audiences (customers, leads, opportunities, etc.).
What’s the biggest mistake people make here?
Importing the list as “create new contacts.”
That’s how databases get messy—and how people end up emailing customers things they already bought.
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