HubSpot Email Deliverability: Fix Low Open Rates in 2026

HubSpot email deliverability depends on which of HubSpot's sending paths an email takes. Marketing emails go out through HubSpot's own network on shared IPs, while sequences and one-to-one sales emails go out through your connected Gmail or Outlook inbox. Each path has its own limits, its own reputation, and its own reasons for landing in spam.

This guide covers how each path works, the limits and thresholds HubSpot documents in its knowledge base, why HubSpot emails end up in spam, how to tell a real deliverability problem from a tracking artifact, and the eight fixes that move open rates back up. Every HubSpot number below links to the HubSpot help article it comes from.

TL;DR

• Two systems: Marketing email uses HubSpot's shared IPs by default. Sequences and one-to-one emails use your connected inbox, so Google or Microsoft controls their reputation and limits.
• Dedicated IP: Requires Marketing Hub Professional or Enterprise plus a paid add-on, and takes 40 days to warm up. Most teams fix more by cleaning lists than by changing IPs.
• Sequence caps: 500 emails per user per day on Professional seats, 1,000 on Enterprise, 350 on a free Gmail inbox. Treat these as ceilings, not targets.
• Suspension lines: HubSpot can suspend marketing email at 5% hard bounces, 0.1% spam reports, or 3% unsubscribes in a month.
• Fix order: Authenticate the domain (DKIM, SPF, DMARC), verify contacts, keep graymail suppression on, lower sequence volume, simplify copy, then monitor and repair.

How HubSpot Sends Email: Three Paths

HubSpot sends email through three different paths, and deliverability problems rarely affect all three at once. According to HubSpot's article on how email sending works in HubSpot, marketing and workflow emails go out through HubSpot's sending network, while one-to-one, sales, and sequence emails go through a connected inbox and never touch HubSpot's IPs.

This split explains most confusing HubSpot deliverability reports. A newsletter can land in spam while sequences reach the inbox, or the reverse. When you troubleshoot, start by naming the path: a marketing email problem points to your sending domain, HubSpot list hygiene, and engagement, while a sequence problem points to the connected inbox, its daily volume, and how its domain is set up in Google Workspace or Microsoft 365.

Shared vs Dedicated IP in HubSpot

HubSpot marketing email uses shared IP addresses unless you buy an add-on. HubSpot's guide to connecting a dedicated IP address lists the requirements: a Marketing Hub Professional or Enterprise subscription plus either the Dedicated IP Address Add-On (for marketing email) or the Transactional Email Add-On (for transactional email).

• Warm-up: Accounts on the Dedicated IP Address Add-On go through a 40-day warm-up before all traffic moves to the new IP. Transactional Email Add-On accounts can use the IP right away.
• Pause rule: If you stop sending for more than 7 days, the warm-up pauses until you resume.
• DNS: A dedicated IP needs its own sending subdomain records, and HubSpot recommends a subdomain such as news.example.com to protect your root domain.

HubSpot describes a dedicated IP as a good fit for accounts that send a high volume of email, but it does not publish a minimum volume. The trade-off is simple: on a shared IP, your reputation is blended with other senders, and on a dedicated IP, your reputation is entirely your own. That helps a large, consistent sender with clean lists. It hurts a sender with irregular volume or dirty data, because there is no pool to absorb the damage.

For most B2B teams, mailbox providers weigh domain reputation and recipient engagement far more than the IP. If your HubSpot emails land in spam today, a dedicated IP will not fix a list that bounces or a domain that is not authenticated. Fix those first, which is what the rest of this guide covers.

HubSpot Sequence and Connected Inbox Limits

HubSpot limits sequence sends per user over a rolling 24-hour period, and your inbox provider's limit applies on top. The figures below come from HubSpot's article on sending limits for connected email accounts.

A few details matter in practice. The limit counts sends, not enrollments, so scheduled follow-ups from earlier enrollments use up the same daily allowance. When several users share one connected inbox, the limit applies to the inbox as a whole. When a user hits the limit, new contacts do not enroll. HubSpot trial accounts do not get the higher limits.

The caps are technical ceilings, not safe sending volumes. A connected inbox that sends 500 cold emails a day looks nothing like a person, and Google and Microsoft judge it that way. Cold email teams typically cap each inbox at 30 to 50 emails a day including follow-ups, as covered in our email deliverability checklist.

HubSpot's Bounce and Spam Thresholds

HubSpot monitors marketing email and can suspend sending when an account crosses its monthly limits. Its article on resolving email sending suspensions lists a 5% hard bounce rate, a 0.1% spam report rate (about one report per 1,000 emails), and a 3% unsubscribe rate in a given month. Repeated stopped sends, complaints sent directly to HubSpot's abuse team, and spam trap hits can also trigger a suspension.

The stakes differ by plan. Suspensions in accounts on HubSpot's free tools cannot be lifted, so the account can no longer send email. Paid accounts can appeal from the Health tab after cleaning their contacts, and HubSpot's deliverability team reviews the appeal. Removing the contacts that bounced is not enough on its own, because HubSpot already suppresses hard bounces, unsubscribes, and spam reporters automatically.

The open rate line comes from HubSpot's sending reputation repair plan, which recommends narrowing your audience when your cumulative open rate consistently falls below 10%.

What Gmail, Yahoo, and Outlook Require

HubSpot's thresholds sit on top of the rules that mailbox providers enforce. All three major providers now require authenticated mail from bulk senders, per Google's email sender guidelines, Yahoo's sender best practices, and Microsoft's Outlook requirements for high-volume senders.

• Gmail: SPF, DKIM, and DMARC for bulk senders, one-click unsubscribe for marketing mail, and a spam rate in Postmaster Tools below 0.1% that never reaches 0.3%.
• Yahoo: The same authentication requirements and a complaint rate below 0.3%.
• Outlook.com: Since May 5, 2025, senders above 5,000 emails a day to Outlook.com, Hotmail, and Live addresses must pass SPF, DKIM, and DMARC, or the mail is rejected with 550 5.7.515.

HubSpot's 0.1% spam report limit lines up with Gmail's target, so a HubSpot account that stays clear of suspension is usually in a safe zone for Gmail too. One caveat: HubSpot can only count the spam reports that mailbox providers pass back to it, and Gmail does not report individual complaints to senders. Check Postmaster Tools for the Gmail rate rather than relying on HubSpot's count alone.

Why HubSpot Emails Land in Spam

HubSpot emails land in spam for the same reasons any email does, but a few causes are specific to how HubSpot accounts get set up and used.

1. No authenticated sending domain. Without one, HubSpot sends using an email variable domain in the From address, which HubSpot itself warns may look suspicious to inbox providers.
2. Stale or unverified contacts. CRMs collect years of form fills, imports, and event lists. People change jobs, mailboxes close, and old addresses bounce or become spam traps. One import of an old list can push a send past the 5% hard bounce line.
3. Emailing unengaged contacts. Mailbox providers watch how recipients react. Sending every newsletter to contacts who have not opened anything in a year trains filters to treat your mail as unwanted.
4. Sequence volume from one inbox. Hundreds of near-identical emails a day from a single Google Workspace or Microsoft 365 inbox looks automated, and the provider throttles or filters it.
5. Cold outreach from the primary domain. Your main domain also carries customer email, invoices, and marketing. Aggressive cold sequences from it put all of that at risk.
6. Heavy HTML and tracking in sales emails. Images, multiple links, and tracking pixels make a one-to-one email look like a campaign. Our guide on how to avoid spam filters covers the content side in detail.
7. Shared IP neighbors. On shared IPs, other senders affect the pool. This is real but usually smaller than the effect of your own lists and engagement.

Low Open Rates: Deliverability or Measurement?

A low HubSpot open rate is a symptom, not a diagnosis. Open tracking depends on a pixel loading, so the number moves when mail lands in spam, but also when Apple Mail Privacy Protection preloads images, when corporate security scanners fetch them, or when tracking is switched off. Match the pattern you see to the likely cause before you change anything.

To confirm spam placement directly, send a campaign to a set of seed addresses at Gmail, Outlook, and Yahoo and see where it lands. Our email deliverability test guide walks through the free and paid ways to run one. If mail reaches the inbox but sits in the Gmail Promotions tab, that is a different problem with different fixes, covered in how to avoid the Gmail Promotions tab.

How to Fix HubSpot Email Deliverability

Work through these steps in order. The first three fix the most common causes and take the least time.

Step 1: Authenticate Your Sending Domain

Connect your email sending domain so HubSpot signs marketing email as you. HubSpot's guide to managing email authentication gives the path:

1. Click the settings icon in the top navigation bar.
2. In the left sidebar, go to Content > Domains & URLs.
3. Open the Email Sending tab and click Connect sending domain.
4. Enter the email address you send marketing email from and confirm the domain.
5. Sign in to your DNS provider if HubSpot supports it, or copy the records manually.
6. Add the two DKIM CNAME records, HubSpot's SPF include, and a DMARC TXT record.

Two details trip people up. First, a domain can only have one SPF record, so add HubSpot's include to your existing record instead of creating a second one. Second, HubSpot marks a domain Authenticated only when DKIM, SPF, and DMARC all verify. A subdomain counts as authenticated if the root domain has a DMARC record. A p=none DMARC policy is enough to start, and you can tighten it once reports show every legitimate sender passing.

Step 2: Authenticate Your Connected Inboxes

Sequences and one-to-one emails rely on the authentication of the inbox that sends them, not on HubSpot's sending domain settings. Confirm that SPF includes Google Workspace or Microsoft 365, DKIM signing is turned on in the Google or Microsoft admin console, and DMARC is published on that domain.

If your reps run high-volume cold outreach, consider sending it from separate, warmed secondary domains instead of the primary domain your marketing and customer email depend on. Our email domain warmup guide covers how to bring a new domain up to volume, and the Instantly HubSpot integration guide shows how teams log replies and lead status from a dedicated sending tool back into HubSpot.

Step 3: Verify Contacts Before They Get Email

Verification is the fastest way to stay under HubSpot's 5% hard bounce limit. Check every address before it joins a marketing list or a sequence, and re-check any list you have not emailed in the last 30 days. Separate the results into valid, invalid, catch-all, and unknown. Send to valid addresses, drop invalid ones, and send to catch-all addresses at low volume or not at all.

Pay special attention to imports. Event lists, partner lists, and old spreadsheets cause most bounce spikes, and HubSpot's stopped-send guidance tells you to remove contacts who did not opt in before you resend. Never import purchased lists into marketing email.

Step 4: Keep Graymail Suppression On

HubSpot's graymail suppression setting, "Don't send to unengaged contacts," is on by default for all marketing emails. It skips contacts who never engaged with the last 11 emails you sent them, or previously engaged contacts who ignored the last 16. Skipped contacts show in the Not Sent report with the reason Unengaged.

Leave it on. If you want to reach those contacts, send them a short re-engagement email as a separate send, then remove anyone who still does not respond. Accounts on Marketing Hub Starter, Professional, or Enterprise can turn the default off, but doing so usually lowers open rates across every send. Suppression relies on open and click data, so it gets less accurate if you turn email tracking off.

Step 5: Set Sequence Limits Below the Caps

On Sales Hub Professional and Enterprise, admins can set a custom daily send limit for connected inboxes, and the custom limit takes precedence over the subscription cap. Set it to a volume that looks human for that inbox, and ramp new inboxes slowly.

• Start new or quiet inboxes low and add volume week by week.
• Enroll contacts in smaller batches through the day instead of one large bulk enrollment.
• Remember that follow-up steps count toward the same daily limit as first emails.
• Pause the sequence for an inbox as soon as bounces or policy rejections appear.

Step 6: Write Sequence Emails Like Real Emails

A sequence email should look like something a person typed. Keep it short and plain, use zero or one link, skip images and attachments, and personalize beyond the first name. If you keep link tracking on for marketing email, a branded tracking domain helps; see our custom tracking domain guide for how tracking links affect placement. For cold first touches, measure replies rather than opens.

Step 7: Monitor the Health Tab and Postmaster Tools

HubSpot's email health tool shows hard bounces, unsubscribes, and spam reports over the past 30 days against benchmarks. Check it after every large send. Pair it with Google Postmaster Tools for each sending domain, which shows the Gmail spam rate HubSpot cannot see. Read bounce codes on sequence emails too: a 5.1.1 is a bad address, while a 5.7.x code points at authentication or policy.

Step 8: Run a Repair Plan When Opens Fall Below 10%

If your cumulative open rate stays below 10%, HubSpot recommends a staged repair plan. Send only to contacts who clicked in the past two weeks. Once the click-through rate reaches 20 to 25%, add contacts who opened in the past four weeks, then widen to six weeks once the open rate reaches 20 to 25%. Step back if either rate drops. HubSpot also advises never sending to contacts who have not opened an email in over a year. For domain-level recovery outside HubSpot, follow our sender reputation guide.

Keep HubSpot Contact Emails Verified with SyncGTM

Most HubSpot deliverability fixes depend on one thing HubSpot does not do natively: checking whether each contact's email still works before you send to it. SyncGTM fills that gap through its HubSpot integration, which syncs contacts, companies, and deals in both directions so verified data lands back in the CRM your team already uses.

1. Pull the contacts you plan to email. Bring a HubSpot list or segment into SyncGTM before a campaign or sequence goes out.
2. Verify every address. SyncGTM checks each email through a multi-provider waterfall at 0.1 credits per address and flags it as valid, invalid, catch-all, or unknown.
3. Recover contacts who moved. For invalid addresses, SyncGTM can check whether the person changed jobs (2 credits) and find their new work email (1 credit per email found; misses are not billed).
4. Write the results back to HubSpot. The 2-way sync updates contact properties, such as a verification status and last-verified date, alongside the corrected email.
5. Filter in HubSpot. Build an active list that excludes invalid and unverified contacts, then use it as an exclusion list for marketing email and a gate for sequence enrollment.
6. Repeat before each campaign. Re-verify lists that have not been emailed in 30 days so bounce rates stay well under HubSpot's 5% line.

For example, verifying a 5,000-contact list costs 500 credits. If 300 of those come back invalid, checking those contacts for job changes costs 600 credits, and finding new emails costs at most 300 credits, since misses are free. HubSpot keeps sending the email; SyncGTM keeps the addresses it sends to accurate.

Conclusion

HubSpot email deliverability gets easier once you treat marketing email and sequences as separate systems. Marketing email depends on an authenticated sending domain, clean lists, and engagement, with HubSpot's 5% bounce and 0.1% spam report limits as the guardrails. Sequences depend on the connected inbox, its domain setup, and volume kept far below HubSpot's 500 and 1,000 daily caps.

Authenticate first, verify contacts second, and let graymail suppression and the repair plan handle engagement. If you are weighing whether HubSpot fits your stack overall, our HubSpot review covers pricing and features by hub.

Ready to stop bounces before they happen? Try SyncGTM free, connect HubSpot, and verify every contact before your next send.