Email is still one of the highest-returning channels in marketing. Litmus puts the average return at around $36 for every $1 spent (Litmus). But that return depends on something many teams take for granted: actually reaching the inbox.
Since early 2024, Gmail and Yahoo have enforced a set of requirements for bulk senders. They are not complicated, but they are strict, and a lot of marketing email still fails them.
Who the rules apply to
Google’s sender guidelines define bulk senders as those sending close to 5,000 or more messages a day to personal Gmail accounts (Google). Yahoo applies similar expectations (Yahoo).
Even if you send less, follow the same practices. Mailbox providers reward good behaviour at every volume.
Rule 1: Authenticate your email
Three DNS records prove your emails are really from you.
- SPF lists the servers allowed to send email for your domain.
- DKIM adds a cryptographic signature that shows the message was not altered.
- DMARC tells mailbox providers what to do if SPF or DKIM checks fail, and sends you reports. Bulk senders need a DMARC policy, at minimum
p=none, and the visible From domain must align with SPF or DKIM.
A common mistake is authenticating the email platform’s domain but not your own. Make sure your sending platform signs with your domain.
Rule 2: One-click unsubscribe
Marketing and promotional emails must support one-click unsubscribe in the email headers, so the mailbox can show an unsubscribe option, and requests must be honoured promptly. A clearly visible unsubscribe link in the body is still expected too.
Making it easy to leave feels counter-intuitive. In practice it protects you: people who cannot unsubscribe easily click “report spam” instead.
Rule 3: Keep spam complaints low
Google asks senders to keep spam rates reported in Postmaster Tools below 0.1% and to avoid ever reaching 0.3% (Google). That is three complaints per thousand emails, which is not many.
The fastest ways to push complaints up:
- emailing people who never clearly opted in;
- sending too often or with no relevance;
- continuing to email people who have not engaged in a long time;
- hiding who the email is from.
Beyond the rules: what actually drives inbox placement
Compliance gets you to the starting line. Inbox placement over time depends on reputation, which is built on engagement.
- List hygiene. Remove hard bounces immediately and sunset contacts who have not engaged for a long period.
- Consistent volume. Sudden spikes look suspicious. Warm up new domains and IPs gradually.
- Relevance. Segment and personalise, so fewer people ignore or report your emails.
- Clear identity. Recognisable sender names and consistent From addresses.
A deliverability checklist
- SPF, DKIM and DMARC set up and aligned with your From domain
- Sending platform signing with your domain, not just theirs
- One-click unsubscribe enabled; unsubscribes processed promptly
- Google Postmaster Tools set up and checked regularly
- Spam rate consistently under 0.1%
- Bounces removed automatically; inactive contacts sunset
- Clear consent records for every subscriber
Where AI helps
AI tools can review DMARC reports and summarise authentication failures, flag segments with rising complaint or bounce rates, and predict which inactive contacts are unlikely to re-engage. They can also check campaign content for spam-like patterns before sending. Decisions about who to remove and how often to send should still be made deliberately.
The takeaway
Deliverability is no longer a technical afterthought. The rules are clear, enforced and measurable. Get authentication, unsubscribes and complaint rates right, then protect your reputation with relevant, well-targeted email.
Deliverability checks are built into our email marketing service. Next, read about the email metrics that still mean something.
