Your business needs to know that emails reach recipients every time. Delivery failures are frustrating at best and a business disaster at worst.
Most delivery failures are not caused by spam content. They are caused by authentication gaps, misaligned domains, or misconfigured infrastructure. This checklist focuses on the areas that actually determine whether your email reaches the inbox.
Why inbox placement is harder than it used to be
Email providers no longer assume your messages are legitimate. They verify them. Authentication, infrastructure, and behaviour are all evaluated together, and failure in any one area is enough to affect delivery.
Authentication has moved from best practice to baseline. SPF (Sender Policy Framework), DKIM (DomainKeys Identified Mail), and DMARC (Domain-based Message Authentication, Reporting and Comformance) are expected, with stricter enforcement for higher-volume senders.
At the same time, reputation is measured continuously. Spam complaint thresholds are defined and monitored, and poor signals are addressed promptly.
Open rates are also less reliable due to privacy protections, shifting the focus toward complaints, engagement, and consistent sending behaviour.
How can you ensure your compay’s mail is delivered?
1. Publish an SPF record
SPF defines which servers are allowed to send email for your domain. Without it, anyone can attempt to send as you.
Check: One SPF record only, including all legitimate sending services. Avoid exceeding the 10 DNS (Domain Name System) lookup limit, which often happens when stacking multiple third-party includes.
2. Enable DKIM signing
DKIM adds a cryptographic signature to each email, proving it was authorised and not altered in transit.
Check: DKIM signing enabled with 2048-bit keys.
Older outbound gateways or legacy SMTP relays may lack support for modern key lengths, which can require software updates or hardware replacement.
3. Publish a DMARC policy
DMARC ties SPF and DKIM together and defines what happens when checks fail. It also provides visibility into who is sending on your behalf.
Check: DMARC record present with reporting enabled. Start with monitoring, then move to enforcement.
4. Ensure domain alignment
The domain in the visible From address must match the domain used for authentication. Passing SPF or DKIM alone is not enough if alignment fails.
Check: SPF or DKIM domain aligns with the From domain.
This is where CRM (Customer Relationship Management) systems, ticketing tools, and marketing platforms most often fail, even when SPF and DKIM are configured.
5. Configure reverse DNS (PTR)
Your sending IP (Internet Protocol) must resolve to a hostname, and that hostname must resolve back to the same IP.
Check: PTR (Pointer Record) matches forward DNS.
For on-premise systems or static IPs, this is often controlled by your ISP (Internet Service Provider) or hosting provider and is frequently missed.
6. Separate email streams
Marketing, transactional, and operational email should not share the same domain or reputation.
Check: Use subdomains to isolate different types of traffic.
This prevents lower-quality traffic from affecting critical messages.
7. Warm up new domains and IPs
New sending identities must build trust gradually. Sudden spikes from a new domain resemble abuse patterns.
Check: Gradual, consistent volume increases over time.
8. Maintain list quality
Invalid addresses, hard bounces, and disengaged recipients damage reputation quickly.
Check: Remove invalid recipients and suppress non-engaging users.
Do not use purchased lists. They introduce high complaint and bounce rates immediately.
9. Make unsubscribing easy
If recipients cannot easily opt out, they will mark your email as spam.
Check: List-Unsubscribe header present and functional.
For bulk senders, one-click unsubscribe is now expected.
10. Monitor your sender reputation
Spam complaints, authentication pass rates, and delivery errors directly affect filtering, throttling, and blocking.
Check: Spam complaint rate consistently below 0.3%.
Reputation issues build gradually but can trigger sudden filtering or blocking.
Ensure a smooth landing every time
If your email ends up in spam, something in your setup is off. It is usually small, often overlooked, and rarely where you expect. Once corrected, the problem goes away.
Sources
Google Email Sender Guidelines; Google Sender Requirements FAQ; Google Postmaster Tools; Microsoft Outlook Sender Requirements; RFC 7208 (SPF); RFC 6376 (DKIM); RFC 7489 (DMARC)
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