Email Deliverability in 2026: A Marketo Checklist for the Inbox
A practical Marketo deliverability checklist covering SPF, DKIM, DMARC, list hygiene, consent, and monitoring so your emails reach the inbox.
You can write the best email of your career, but it does nothing if it lands in spam. Mailbox providers have steadily raised their expectations of bulk senders, and the gap between careful senders and careless ones keeps growing. This checklist covers what Marketo teams should have in place to reach the inbox reliably.
Key takeaways
- Authentication with SPF, DKIM, and DMARC is the baseline, not a bonus.
- Engagement and list hygiene shape your sender reputation more than any single email.
- Easy unsubscribes and clear consent protect both your reputation and your brand.
- Monitor deliverability continuously, not only when something breaks.
1. Authenticate your sending domain
Authentication proves to mailbox providers that you are who you say you are. In Marketo, this means setting up three records with your IT or DNS team:
- SPF: tells receiving servers which systems are allowed to send on behalf of your domain, including Marketo.
- DKIM: adds a cryptographic signature to your emails. Configure a custom DKIM domain in Marketo Admin so messages are signed with your own domain.
- DMARC: tells providers what to do with messages that fail authentication and sends you reports. Start with a monitoring policy, review the reports, then move toward a stricter policy.
Major mailbox providers now expect bulk senders to have authentication and alignment in place. If you have not reviewed your records recently, make it the first item on your list.
2. Use branded links and a clean sending setup
Set up a branded tracking domain (a CNAME on your own domain) so links in your emails point to your brand rather than a shared default. This looks more trustworthy to recipients and keeps your reputation tied to your own domain.
High-volume senders should also talk with Adobe about whether a dedicated IP makes sense. A dedicated IP gives you full control over your reputation, but it also needs consistent volume and a proper warm-up plan. For many teams, a well-managed shared pool is perfectly appropriate.
3. Keep your list healthy
Your sender reputation reflects how recipients respond to you. Sending to people who never open, never click, or no longer exist tells providers your mail is unwanted. Build hygiene into your regular operations:
- Never send to purchased or rented lists.
- Suppress hard bounces and review addresses that soft bounce repeatedly.
- Define an inactive audience (for example, no engagement over an agreed period) and stop mailing them, or run a short re-engagement program first.
- Validate addresses at the point of capture, and use confirmation where it fits your audience.
Deliverability is not a setting you switch on. It is the sum of every sending decision you make.
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4. Respect consent and make leaving easy
It sounds backward, but making it easy to unsubscribe improves deliverability. When people cannot find the unsubscribe link, they click “report spam” instead, and spam complaints damage reputation far more than an opt-out ever will.
- Keep a visible unsubscribe link in every marketing email.
- Support one-click unsubscribe headers for bulk mail, as mailbox providers expect.
- Offer a preference center so people can choose topics or frequency instead of leaving entirely.
- Process opt-outs promptly and keep your CRM in sync so sales tools respect them too.
5. Send with care
How you send matters as much as who you send to. Use Marketo communication limits to cap how many marketing emails a person can receive in a day and a week. This protects your audience from overlapping programs that each seemed reasonable on their own.
Keep content clean: a sensible balance of text and images, accurate subject lines, alt text on images, and no misleading claims. Segment your sends so people receive messages relevant to them. Relevance drives engagement, and engagement drives inbox placement.
When launching a new domain, IP, or large audience, ramp volume gradually and start with your most engaged contacts.
6. Monitor continuously
Do not wait for a sales rep to tell you prospects are not receiving emails. Build a monitoring routine:
- Review bounce, unsubscribe, and spam complaint trends by program and by audience.
- Register for the postmaster and feedback tools that major mailbox providers offer.
- Read your DMARC reports to spot unauthorized senders or misconfigured systems.
- Consider seed testing or a deliverability tool for inbox placement visibility.
Deliverability is one area a Marketo instance health check should always cover, because problems often hide in settings no one has looked at for years.
Frequently asked questions
Why are my Marketo emails going to spam suddenly?
Common causes include a change in authentication records, a send to an old or unengaged list, a spike in complaints, or content that triggers filters. Check your DNS records first, then review recent sends for unusual audiences.
Do I need a dedicated IP in Marketo?
Not necessarily. Dedicated IPs suit high, consistent volume. Lower-volume senders often do better on a well-managed shared pool. Talk with Adobe about your sending patterns before deciding.
Does DMARC affect deliverability on its own?
DMARC is part of the authentication picture providers expect. On its own it does not guarantee inbox placement, but missing or broken authentication can hurt it.
If you are not sure whether your instance passes this checklist, a Marketo Health Check will review your authentication, sending setup, and list hygiene and give you a prioritized plan to protect the inbox.
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