Most marketers obsess over creative, but overlook the basics of email deliverability. If your messages aren’t hitting the inbox, every campaign is wasted effort—no matter how clever the copy or design.

This guide breaks down exactly what drives deliverability, the technical steps that matter, and how to make every send count.

What is email deliverability?

Email deliverability is about more than just a successful “send.” True deliverability is getting your marketing emails into inboxes—where people actually see them—not trapped in spam or filtered tabs. Inbox placement is the metric that matters, not just “delivered” status in your email platform.

Achieving strong deliverability means combining technical best practices with ongoing data discipline. Every major ISP—Gmail, Outlook, Telstra, Bigpond, and others—uses its own filtering systems. What works for one may fail with another. The only way to stay ahead is by keeping your approach agile and evidence-based.

The three pillars of effective email deliverability

1. List hygiene: protect your reputation at the source

Deliverability problems nearly always start with poor data. If you let list quality slip, your sender reputation and campaign results will follow.

Key risks and fixes:

• Unfiltered list imports: Moving old lists to platforms like Salesforce Marketing Cloud without removing bounced or disengaged addresses? You’re asking for trouble. Segment and clean every list before you send.

• Low-quality data sources: Not all email addresses are created equal. Emails captured via e-commerce checkout are usually valid and engaged. Addresses written on paper at events or entered in competitions are often risky. Use confirmed (double) opt-in where needed.

• Neglected data decay: Especially in B2B, lists degrade rapidly. People change jobs, businesses close, and ISPs recycle abandoned addresses as spam traps. Ongoing list validation is essential.

• Ongoing maintenance: List hygiene isn’t a launch task—it’s constant. Remove unsubscribes straight away. Regularly review for inactivity and decide whether to segment or suppress old contacts. Use your CRM to track last engagement and automate as much as possible.

2. IP warming: build sender trust, step by step

If you start sending high volumes from a new or dormant IP address, ISPs see risk—not trust. IP warming is how you avoid deliverability disasters.

How to do it well:

• Start with your best: Begin with your most engaged recipients—those who open and click. Early positive engagement is crucial.

• Increase volume gradually: Scale up send volume over several weeks, not days. Monitor bounce rates, complaint rates, and open rates at every stage.

• Watch by domain: Different ISPs behave differently. If your database skews heavily to Gmail, Outlook, or Bigpond, track those domains separately. Adjust your send plan for any negative signals.

• Monitor technical feedback: Track hard and soft bounces, sender reputation scores, and blocklists. Pause and review if you see any drop-off.

IP warming is not just technical process—it requires hands-on management and the willingness to adapt if metrics move the wrong way.

3. Engagement signals: what ISPs actually look for

Strong deliverability doesn’t end with good data and an authenticated sender. Inbox providers constantly watch how recipients interact with your emails.

ISPs favour:

• High open and click rates

• Positive actions (replies, moving messages to inbox, adding to contacts)

• Consistent engagement over time

ISPs penalise:

• Spam complaints

• Emails deleted without being read

• High unsubscribe rates

• Ongoing inactivity

Remember: inbox providers like Gmail go deeper than your standard metrics. They measure how long someone views your message and whether it’s read or scrolled past. You can’t see this directly, but declining engagement will show up as slipping inbox placement.

Practical tip: Don’t just push offers. Balance your content—alternate between clear asks (buy, donate, register) and genuine value-adds (how-tos, guides, case studies, customer stories). Segment your lists so you’re only sending high-frequency campaigns to those who want them.

Technical essentials: the non-negotiables

• Authentication: Set up SPF, DKIM, and DMARC to prove you’re a legitimate sender and protect against spoofing.

• Bounce management: Remove hard bounces immediately. Monitor and suppress addresses that repeatedly soft bounce.

• Email validation: Use a validation tool on large imports or old data to avoid obvious issues.

• Automated sunset policies: Decide when a subscriber is inactive and set up automatic suppression or re-engagement streams.

The bottom line

Email deliverability isn’t a one-off fix—it’s an ongoing discipline. Quality data, careful IP management, and strong engagement drive long-term inbox placement. Miss any one of these, and your email marketing results will stall.

Ready for your next campaign to reach the inbox and actually deliver results? Get in touch today to take control of your deliverability.