Key takeaways
- Authenticate the sending domain with SPF, DKIM, and an appropriate DMARC policy.
- Clean invalid, disposable, duplicate, and suppressed addresses before a high-volume send.
- Monitor bounces, complaints, unsubscribes, engagement, and provider-specific signals together.
- Start with your most engaged audience when warming a new domain or stream.
- Use verification to reduce avoidable address risk, but remember that consent and relevance still drive delivery.
Email deliverability is the ability to reach the inbox rather than the spam folder, a quarantine folder, or a rejected queue. It depends on the relationship between your sending identity, your recipient data, your message, and the behavior of the people receiving it.
Use this checklist before a campaign, after moving to a new provider, and whenever your bounce or complaint rate changes unexpectedly.
1. Authenticate your sending domain
Start with the technical foundation:
- Publish SPF for the services authorized to send on your behalf.
- Enable DKIM signing and confirm the signing domain is aligned with your From domain where required.
- Publish a DMARC record and review reports before moving to a stricter enforcement policy.
- Use TLS for message transmission.
- Make sure forward and reverse DNS are configured for dedicated sending infrastructure.
Google’s current sender guidance lists authentication, valid forward and reverse DNS, TLS, message formatting, and complaint control among the requirements and recommendations for mail sent to Gmail accounts (Google). Authentication is not a substitute for permission, but without it your other work has a weaker foundation.
2. Protect the address data
Before uploading or syncing a list, check:
- Syntax errors and accidental spaces.
- Domains that do not exist or cannot receive email.
- Disposable addresses that are unsuitable for a long-term relationship.
- Role-based addresses such as info@ or support@ that need a different owner.
- Catch-all or risky addresses that should be segmented.
- Previous hard bounces and unsubscribes.
- Duplicate rows that would cause multiple sends to one recipient.
Verification is most effective before the list enters your sending platform. VeriMailX supports real-time checks for new contacts and bulk CSV verification for existing lists, so the same policy can be applied at collection and campaign time.
3. Confirm permission and expectations
A deliverable address is not automatically a permissioned address. Record how the contact joined the list, what they agreed to receive, and which brand or sender they recognized. Remove addresses that have unsubscribed or that you are not legally allowed to contact in your jurisdiction.
Set expectations with a clear From name, a recognizable subject, and a visible unsubscribe path. People who understand why they received a message are less likely to mark it as spam.
4. Segment before sending
Do not treat the whole database as one audience. Separate new subscribers, recent engagers, dormant contacts, customers, prospects, role accounts, and unresolved risk. Start a campaign with the segment most likely to open and click, then expand only if the early signals are healthy.
For a new domain or sending stream, a smaller engaged audience gives providers cleaner evidence about the quality of the mail. A sudden blast to every historical record makes it difficult to identify which segment caused the problem.
5. Review content and links
Check that the From address is aligned with the brand, links use trusted domains, images have useful alt text, and the message is readable on a phone. Avoid misleading subject lines, excessive urgency, and link shorteners that obscure the destination.
Every campaign should have a clear reason to exist. A technically perfect message can still be reported as spam if recipients do not recognize the sender or understand the value.
6. Monitor the right signals
Track at least:
| Signal | What it can reveal |
|---|---|
| Hard bounce rate | Invalid, stale, or suppressed addresses were mailed |
| Soft bounce rate | Temporary capacity, throttling, or mailbox conditions |
| Spam complaints | Recipients do not trust or want the message |
| Unsubscribe rate | The audience or frequency is misaligned |
| Opens and clicks | Engagement and audience quality, with privacy caveats |
| Deferrals and blocks | Provider reputation or policy problems |
Look for changes by provider, domain, campaign, and segment. A healthy aggregate number can hide a serious problem at one mailbox provider.
7. Keep a suppression system
Suppress hard bounces, unsubscribes, spam complaints, legal opt-outs, and addresses that your team has explicitly marked as do-not-contact. Keep suppression data available to every sending tool so a contact cannot re-enter through a separate import.
Klaviyo’s current list-cleaning guidance recommends identifying unengaged profiles, excluding them from most sends, and suppressing contacts who never engage after an appropriate re-engagement attempt (Klaviyo). The specific time window should match your sending cadence and customer lifecycle.
8. Use a preflight routine
Before pressing send, ask:
1. Is the sending domain authenticated and aligned? 2. Are all unsubscribes and hard bounces suppressed? 3. Has the list been checked recently enough for its age? 4. Are risky and unknown rows excluded or governed by a deliberate policy? 5. Is the audience expecting this message? 6. Is the volume appropriate for the domain’s history? 7. Are the links, reply address, and unsubscribe path working?
Save the answers with the campaign. A repeatable checklist turns deliverability from guesswork into operations.
The bottom line
Good deliverability comes from many small controls working together: authentication, permission, relevant content, clean data, reasonable volume, and fast suppression. Use verification to remove avoidable address risk, then let engagement and recipient trust guide the rest of the program.
Sources
- Google: Email sender guidelines
- Klaviyo: How to clean your email list
- Google: Gmail sender compliance data
Frequently asked questions
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