Email Deliverability Checklist for 2026: 11 Checks

An email deliverability checklist is not a spam-word scan. In 2026, inbox placement is mostly a trust problem: whether your domain is authenticated, whether recipients wanted the email, whether you honor unsubscribes quickly, and whether your sending pattern looks stable.

If your campaigns suddenly land in spam, do not start by rewriting every subject line. Start with the infrastructure, the list, and the way the campaign is being sent. This guide gives you the checks to run before a major send, after an email marketing migration, or when open and click performance drops for reasons your copy cannot explain.

Editorial note: This checklist was reviewed against Google's email sender guidelines, Google's sender FAQ, Spamhaus guidance on marketing email and sunset policies, and recent Sinch Mailgun deliverability research.

Email deliverability checklist: quick version

Use this version before a campaign, migration, promotion, product launch, or major list import.

If several of these checks are hard to run in your current tool, the problem may be platform fit. Compare the usual decision points in ActiveCampaign vs Mailchimp, Klaviyo vs Mailchimp, HubSpot vs Mailchimp, and Mailchimp vs Constant Contact.

Email deliverability checklist for sender requirements

The technical floor has moved up. Google says all senders to Gmail should authenticate with SPF or DKIM, while bulk senders to personal Gmail accounts need SPF, DKIM, and DMARC. Google also expects bulk senders to keep spam rates low and support one-click unsubscribe for marketing and subscribed messages.

Google's FAQ defines a bulk sender as a sender that gets close to 5,000 messages or more to personal Gmail accounts in a 24-hour period. It also says domains that reach that status remain classified as bulk senders. Even if you are below that level, the practical takeaway is simple: treat authentication, unsubscribe handling, and complaint control as normal setup, not advanced deliverability work.

1. Confirm SPF for every sending source

SPF tells receiving mail servers which systems are allowed to send email for your domain.

Check every active sender:

• Your email marketing platform
• Your CRM
• Your transactional email tool
• Your support desk
• Your ecommerce platform
• Any sales engagement or outbound tool

Then remove old senders. Old SPF includes are common after tool changes. If a platform no longer sends email for you, it should not stay in your SPF record forever.

For a simple newsletter business, this may be one ESP and Google Workspace. For a B2B SaaS company, it may be HubSpot, Salesforce, Intercom, a transactional provider, and a sales sequencing tool. If you are still mapping the broader stack, our B2B SaaS marketing stack analysis shows why CRM, support, analytics, and automation choices need to be read together.

2. Turn on DKIM and verify it passes

DKIM signs messages so mailbox providers can verify that the email came from an approved sender and was not altered after it left the sending platform.

Do not assume DKIM is working because the ESP shows a green status during setup. Send a real test message, inspect the headers, and confirm the DKIM result passes for the domain you expect. If you use multiple tools, repeat this for each one.

This matters during migrations. A team may authenticate Mailchimp correctly, move to another platform, then send from the new account before DKIM is finished. If the move is already planned, use the email marketing migration checklist before launch.

3. Publish DMARC and check alignment

DMARC connects authentication to the domain people see in the From address. Google says bulk senders need a DMARC record, and its FAQ says the From domain must align with either SPF or DKIM for direct mail to personal Gmail accounts.

At minimum, publish a DMARC record and monitor results. A p=none policy may satisfy the minimum rule, but it is mostly a monitoring state. Once you know all legitimate senders pass authentication, work with your technical team toward stricter enforcement.

Do not rush this if several systems send email for the domain. A strict DMARC policy before discovery can break real mail from sales, support, billing, or product notifications.

4. Support one-click unsubscribe

One-click unsubscribe is not the same as a footer link to a preferences page. For Gmail, it is implemented with List-Unsubscribe headers that meet the relevant standard. Google says promotional and marketing messages need this when the sender is in the bulk-sender category, and its FAQ says normal mailto links do not satisfy the one-click requirement.

Your ESP should handle this. If it does not, or if it only adds one-click unsubscribe on some plans, factor that into platform selection. This is especially important for high-volume newsletters, ecommerce promotions, and SaaS lifecycle programs.

Keep the visible unsubscribe link too. A clear body link lowers friction and gives annoyed recipients a clean exit before they report the message as spam.

5. Keep complaint rates low

Google's sender FAQ says senders should keep user-reported spam rates below 0.1% and prevent them from reaching 0.3% or higher. That is a useful operating target even outside Gmail.

Complaint control is not only a technical issue. It comes from list source, expectation setting, frequency, content relevance, and easy opt-out. If someone subscribed to a product update, then receives daily promotions, the authentication can be perfect and the complaint risk can still be high.

Email deliverability checklist for list quality

Spamhaus puts the deliverability principle plainly: send authenticated, targeted mail to an engaged audience. That means list quality is not a cleanup task you do once per year. It is part of the sending system.

6. Separate sendable contacts from stored contacts

Your database is not your audience.

Split contacts into these groups before a campaign:

• Subscribed and recently engaged
• Subscribed but inactive
• Unsubscribed
• Hard bounced or invalid
• Suppressed because of complaints
• Non-subscribed contacts, such as checkout records or CRM records
• Customers who should receive transactional mail but not promotional mail

This prevents a common mistake: exporting a CRM or ecommerce database, importing it into a new email tool, and treating every row as marketable. It also affects price. Some tools count old or non-subscribed records differently, so list cleanup can change both deliverability and cost. See email marketing contact billing before you import everything into a new plan.

7. Use a sunset policy for inactive contacts

A sunset policy removes or suppresses contacts who have stopped engaging. Spamhaus warns that old, unengaged addresses can hurt reputation, create spam-trap risk, and raise complaints when stale lists are reactivated.

The exact cutoff depends on your cadence. A daily ecommerce sender should not wait as long as a quarterly nonprofit newsletter. As a practical starting point:

• Put 90-day non-clickers into a lower-frequency segment
• Put 180-day non-engagers into re-engagement or suppression
• Treat 12-month inactive contacts as high risk unless they are customers with a clear relationship

Do not send a re-engagement campaign to every inactive contact at once. Stagger it, watch complaints and bounces, and stop if the segment reacts poorly.

8. Clean contacts before a platform migration

Moving to a better platform does not reset a bad list. It can make the problem worse because you are sending from new infrastructure while importing old risk.

Before switching tools:

• Export unsubscribes and suppressions separately
• Remove hard bounces and obvious invalid records
• Preserve consent source and opt-in date where available
• Keep inactive contacts out of the first launch send
• Start with recent clickers, buyers, active leads, or active customers

This is especially important when moving from a simple tool to a deeper one. If you are choosing because automation is the problem, compare ActiveCampaign vs Mailchimp. If ecommerce data is the reason, compare Klaviyo vs Mailchimp. If the issue is CRM and sales handoff, compare HubSpot vs Mailchimp.

Email deliverability checklist before each campaign

Once the foundation is set, each campaign still needs a smaller pre-send check.

9. Send to the right segment first

If the campaign is important, do not send it first to the coldest part of the list.

Start with a segment that has given recent positive signals:

• Clicked recently
• Bought recently
• Filled a form recently
• Replied recently
• Logged into the product recently
• Attended a webinar or event recently

This is useful after migrations, domain changes, tracking-domain changes, new templates, or a long sending pause. Google's sender guidelines also warn against sudden volume spikes and recommend increasing volume gradually after major infrastructure or header changes.

10. Check the message itself

Content is rarely the only cause of deliverability problems, but it can still hurt a marginal sender.

Before sending:

• Use a clear From name that matches the brand
• Avoid misleading subject lines
• Make every link visible and expected
• Use your own domain for key links where possible
• Keep the footer complete with business identity and unsubscribe
• Test mobile rendering
• Test the plain-text version if your ESP sends one
• Check that personalization fields cannot render as blanks or broken merge tags

This is also where category fit matters. A small services business sending one newsletter a month has a different risk profile than a Shopify store sending abandoned cart, browse abandonment, post-purchase, and win-back flows. For ecommerce context, read the ecommerce email marketing stack sample and the abandoned cart email guide.

11. Watch provider-level results

A single average open rate hides the diagnosis.

Look at results by mailbox provider when possible:

• Gmail
• Yahoo and AOL
• Microsoft and Outlook
• Apple domains
• Business domains

If only Gmail drops, review Google Postmaster Tools, authentication, spam complaints, and Gmail-specific rejections. If every provider drops after a list import, list quality is more likely. If one campaign underperforms while the rest are normal, the segment, offer, subject, timing, or links may be the issue.

Sinch Mailgun's deliverability research is a good reminder that delivery rate and inbox placement are not the same. A message can be accepted by a receiving server and still land in spam. That is why serious programs monitor more than "delivered" counts.

When deliverability means you should switch tools

Do not switch platforms because one campaign had a bad week. Fix the basics first.

Switching starts to make sense when the current platform cannot support the operating discipline you need:

• You cannot authenticate a branded sending domain cleanly
• You cannot add or confirm one-click unsubscribe support
• Suppression handling is unclear or manual
• Segmentation cannot isolate engaged, inactive, and risky contacts
• Reporting cannot separate Gmail, Yahoo, Microsoft, and Apple performance
• Automation limits force you to blast broad lists instead of triggering relevant messages
• Contact billing pushes you to keep risky contacts active because cleanup is painful

At that point, the deliverability issue is also a buying issue. Use how to choose an email marketing platform for the broader framework, then compare the likely shortlist:

• Mailchimp vs Constant Contact for simple small-business campaigns
• ActiveCampaign vs Mailchimp for deeper automation and list management
• Klaviyo vs Mailchimp for ecommerce data and lifecycle flows
• HubSpot vs Mailchimp for CRM, sales handoff, and marketing contacts
• Brevo vs Mailchimp for send-volume pricing and multi-channel value

If you are already frustrated by pricing, automation, ecommerce data, or CRM gaps, read signs you have outgrown your email marketing tool before renewing another year.

Frequently Asked Questions

What is email deliverability?

Email deliverability is the ability of your email to reach the inbox instead of spam, junk, quarantine, or a blocked state. It is different from delivery rate, which often only means the receiving server accepted the message.

What is the most important email deliverability check?

Start with authentication and list quality. SPF, DKIM, and DMARC help prove the sender is legitimate, but they do not save a bad list. A clean, consent-based, engaged audience is still the main driver of long-term inbox placement.

Does DMARC guarantee inbox placement?

No. DMARC helps mailbox providers trust that the visible From domain is authorized. It does not guarantee that recipients want the email, that the content is relevant, or that the sender has a strong reputation.

What spam complaint rate is safe?

Google says senders should keep user-reported spam rates below 0.1% and prevent them from reaching 0.3% or higher. Treat 0.1% as the operating warning line. If complaints are rising, reduce volume, narrow the audience, check consent source, and make unsubscribe easier.

How often should I clean my email list?

Review list quality monthly if you send weekly or more often. Review it before every major campaign, list import, platform migration, or reactivation send. For high-volume ecommerce or SaaS lifecycle programs, suppression and engagement rules should run continuously.

Can switching email marketing platforms fix deliverability?

Sometimes, but only if the old platform limited authentication, segmentation, suppression, reporting, or relevant automation. Switching does not fix poor consent, old contacts, sudden volume spikes, or a damaged domain reputation by itself.

Next steps

Use this email deliverability checklist before changing software. If the checks show that your current setup is the problem, move to the comparison that matches the root cause:

• Automation and lifecycle complexity: ActiveCampaign vs Mailchimp
• Ecommerce segmentation and revenue flows: Klaviyo vs Mailchimp
• CRM and sales handoff: HubSpot vs Mailchimp
• Simple campaigns and small-business email: Mailchimp vs Constant Contact
• Lower-cost multi-channel sending: Brevo vs Mailchimp

If you are still choosing the category, start with best email marketing software, best ecommerce email marketing, or CRM email marketing software.