Email Deliverability Optimization

What deliverability optimisation means

Delivery and deliverability are different things. Delivery means the receiving server accepted your message. Deliverability means it reached the inbox rather than the spam folder or a quiet filter. A message can be accepted and still never be seen.

Mailbox providers decide placement based on authentication, the reputation of your sending domain and IP, how recipients engage with your mail, complaint signals and, to a lesser degree, content. Optimisation means finding which of those is holding you back, rather than changing everything at once and hoping.

Warning signs

• Open or click rates falling steadily without a change in content.
• Customers saying they found your emails in spam, or never received them.
• One provider performing much worse than the others.
• A rising spam rate in Google Postmaster Tools, or a poor status in Microsoft SNDS.
• Deferrals mentioning reputation, policy or rate in your logs.

Sometimes there is no single dramatic sign, just a slow decline over months. That pattern usually points to list ageing or falling engagement rather than a technical break, and it is worth investigating before it becomes a sharp drop.

What the audit covers

How we work

1. Collect evidence: DNS records, raw headers from test sends, logs, platform reports and reputation dashboards.
2. Diagnose: identify the causes, ranked by impact, with the reasoning written down.
3. Agree the plan: you see a prioritised list before we change anything.
4. Implement: fix authentication and infrastructure first, then list and engagement practices.
5. Rebuild reputation where needed, with a gradual sending plan focused on engaged recipients.
6. Measure: track placement signals and provider dashboards over the following weeks, not just acceptance.

What we won’t do

Deliverability work improves how legitimate mail is received. It is not about tricking filters. We won’t recommend hidden text, misleading subject lines, domain hopping or IP rotation to escape a bad reputation, and we won’t work with purchased or scraped lists.

What you receive

• A written diagnosis explaining what we found, with evidence such as headers, report screenshots and log excerpts.
• A prioritised fix list ranked by expected impact and effort, so the important changes come first.
• Implemented fixes for the items we agree to handle, with a record of each change.
• Sending recommendations covering segmentation, frequency, re-permission and sunset policies.
• A follow-up review after a few weeks comparing provider dashboards and engagement against the starting point.

The diagnosis is written for decision-makers as well as technical staff, because many deliverability fixes involve marketing and data decisions, not just DNS.

What affects timeline and cost

• Number of sending sources, platforms and domains.
• How much evidence is available: logs, reports, dashboard access.
• Whether the fix is mostly technical or requires list and process changes.
• How damaged the reputation is, which sets the pace of recovery.
• Whether we implement fixes or your team does with our guidance.

Common mistakes

Rewriting content repeatedly while an authentication failure goes unnoticed. Switching providers to escape a reputation problem that follows the domain. Continuing to mail years-old inactive subscribers. Judging success by delivery rate, which only shows acceptance. Moving DMARC to reject before every source aligns.

Start with the email infrastructure guide. Related: email authentication, blacklist troubleshooting, all email infrastructure services. Contact us for an audit.

Frequently asked questions