If you searched this, you've probably already done the obvious thing: checked that your domain is connected in HubSpot and seen the reassuring green checkmarks. So the frustrating part is that everything looks right and the mail still isn't landing.
The reason is simple and worth saying plainly before anything else: passing authentication is not the same as landing in the inbox. Authentication (SPF, DKIM, DMARC) proves the mail really came from you. Placement is a separate judgement Gmail and Outlook make about whether people want your mail. You can pass every check and still get filtered. So the question isn't "is my setup verified" - it's "which of the five usual causes is hitting me," and they're rarely the one people expect.
When HubSpot mail goes to spam, the instinct is to re-check DNS. But if your domain was connected weeks ago and worked, your DNS almost certainly didn't change. The far more common cause is your list and your engagement - sending to addresses that bounce or never open. That's invisible in HubSpot's connection screen, which is exactly why it gets missed.
1. First, is it actually spam - or the Promotions tab?
Worth thirty seconds before you change anything, because the fix is completely different. Open Gmail and look at where the mail landed. If it's in the red Spam folder, that's a real deliverability problem and the rest of this article applies. If it's sitting under the Promotions tab, that's Gmail sorting bulk marketing mail into its own bucket - and for newsletters and campaigns, that's often the correct, expected place.
People burn weeks trying to drag marketing mail into Primary. For a one-to-one sales email, you genuinely can: strip the images, lose the big CTA button and the marketing footer, send something that looks like a person typed it, with one link or none. For a designed newsletter blast, Promotions is where Gmail puts that kind of mail for everyone, and forcing it usually isn't worth the effort. Know which problem you actually have.
2. "Connected" doesn't mean DKIM is aligned
Here's a HubSpot-specific subtlety. There are two ways your mail can leave HubSpot, and they authenticate differently:
- Sent through HubSpot's shared infrastructure with their connected-email setup - the common case for marketing email.
- Sent with a dedicated IP and your own connected sending domain.
The trap is DMARC alignment. DMARC passes only when the domain that signed your DKIM (or the SPF return-path) matches the domain in your visible From: address. It's possible to have DKIM technically valid but signed by a HubSpot domain rather than yours - the signature is real, but it doesn't align, so DMARC still fails. HubSpot's green checkmark confirms the record resolves; it does not confirm alignment.
Don't trust the dashboard. Send yourself a test, open it in Gmail, click the three dots → Show original, and read the SPF, DKIM and DMARC lines. You want DKIM = PASS and the signing domain to match your From: domain. If DKIM passes but DMARC says fail, that's an alignment problem, not a missing record - and you fix it by making sure HubSpot is signing with your connected domain.
3. The cause hiding in plain sight: list rot
This is the single most common reason established HubSpot senders suddenly start hitting spam, and it has nothing to do with HubSpot at all.
Email lists decay. People change jobs, abandon addresses, and mistype during sign-up. Industry rule of thumb is that a B2B list loses around a quarter of its addresses to decay every year. When you send to those dead addresses, two bad things happen: you rack up hard bounces, and worse, you hit spam traps - addresses that mailbox providers plant specifically to catch senders mailing lists they shouldn't be. A few trap hits and your domain reputation drops; once that happens, Gmail filters even your good mail.
It compounds. Low engagement (few opens, few replies) tells Gmail your mail isn't wanted, which lowers placement, which lowers engagement further. A single careless import of an old or purchased list can undo months of careful sending in a week.
Clean every list before it goes into HubSpot. Remove invalid syntax, disposable domains, role-based addresses (info@, sales@), and obvious traps, so you never send to an address that bounces. This is the highest-leverage thing most senders can do, and it's also the cheapest. You can run a list through our List Cleaner for free before import - it flags exactly the addresses that will hurt you.
4. Domain and IP reputation
Reputation is the running score mailbox providers keep on you, built from your bounce rates, complaint rates, engagement, and whether you show up on blacklists. It's slow to build and quick to damage.
Two things to check directly. First, are you on a blacklist? If your domain or sending IP landed on a real-time blacklist (RBL) - usually from a past spam incident, a compromised account, or that bad-list import - some providers will reject or filter your mail outright. Second, did you send a sudden volume spike? Going from 500 emails a week to 50,000 overnight looks exactly like a compromised account to a spam filter. Ramp gradually.
If you've moved onto a dedicated IP hoping it would help, and you're sending under roughly 100,000 emails a month, it's probably hurting you. A dedicated IP starts from zero reputation and needs weeks of careful warming; below real volume you never generate enough signal to build trust, and you'd be better off on HubSpot's shared pool which already carries an established reputation.
5. Content and the "looks like spam" signals
Once list and reputation are healthy, content is the last lever. Spam filters in 2026 are mostly engagement-driven, not keyword-driven - the old "don't say free" advice is largely a myth now - but some patterns still hurt:
- One giant image with little text. Image-only emails are a classic spam pattern and filters treat them with suspicion.
- Link mismatches and URL shorteners. Visible text saying one URL while the link points elsewhere, or bit.ly-style shorteners, both raise flags.
- A brand-new sending domain with no history, suddenly blasting volume.
- No working unsubscribe. Required by Gmail and Yahoo's rules - one-click unsubscribe must work, or you're penalised.
If you want to see how a specific message scores before you send it, our Spam Score Checker runs it through the same kinds of rules filters use and tells you what's pulling the score down.
6. How to diagnose which one is your problem
You don't have to guess. Run this quick separation test:
Send a test to fresh inboxes you control - a Gmail, an Outlook, a Yahoo address - that have never interacted with your mail. If those land in the inbox and pass authentication, your configuration is fine and your problem is list and engagement (sections 3 and 4). If those test sends fail authentication or hit spam everywhere, you have a setup or reputation problem (sections 2 and 4).
That single test cuts the problem space in half. From there:
- Configuration suspected → verify your DNS against HubSpot's exact spec with our CRM DNS Verifier, which checks the records HubSpot actually requires, not generic ones.
- Reputation suspected → run a Blacklist Sweep across 12 RBLs to see if you've been listed.
- List suspected → run the list through the List Cleaner and look at how many addresses come back invalid. A high percentage is your answer.
7. The order to fix things in
If you do nothing else, do these in this sequence, because each one builds on the last:
- Clean the list first. Stop sending to addresses that bounce. Nothing else matters until this is true.
- Confirm DKIM alignment via Show Original, not the dashboard. Fix it if DMARC fails.
- Check for blacklisting and stop any volume spikes.
- Re-engage or sunset contacts who haven't opened in 90+ days - mailing the unengaged drags your whole reputation down.
- Then tune content.
Most "HubSpot is sending my mail to spam" problems are solved by the first two steps. HubSpot is rarely the actual problem - it's a very good sender. What lands you in spam is almost always what you're putting into it.