What Is Email Deliverability?
Email deliverability describes how reliably your emails make it through to the inbox of each subscriber on your list. It is not the same as email delivery. Delivery simply means the receiving server accepted the message without generating a bounce. Deliverability goes further and asks where that accepted message actually landed: in the primary inbox, in promotions, in spam, or in some other filtered folder the subscriber will never check.
Inbox providers like Google, Microsoft, and Apple Mail use complex algorithms to decide the fate of every incoming message. These algorithms evaluate signals from multiple sources simultaneously. Your sender reputation, built from your historical sending behaviour, is the most influential single factor. But the algorithms also examine your email authentication records (SPF, DKIM, and DMARC), how engaged your subscribers are, your spam complaint rate, your bounce rates, and the content of the message itself, including whether it contains suspicious links, misleading subject lines, or patterns associated with known spam campaigns.
The key distinction South African businesses often miss is that you can have near-zero bounces and still suffer terrible deliverability. If a large proportion of your emails are landing in the Gmail Promotions tab or the Outlook Junk folder, they are effectively invisible to most subscribers. Those placements translate directly into lower open rates, lower click rates, and ultimately lower revenue from the channel, regardless of how good your content might be.
Email Deliverability In Practice
The scenario below is an illustrative example, not a Juicy Designs client result. The figures indicate the scale of effect that email deliverability issues typically produce, so treat them as indicative rather than measured.
Consider a Cape Town-based e-commerce brand that runs a Black Friday sale campaign and sends to its full list of around 40,000 subscribers. The email service provider might report a delivery rate of around 97%, which looks healthy. But a review of Google Postmaster Tools could show the complaint rate climbing to something in the region of 0.15% and the domain reputation dropping from "High" to "Medium" during the send. The likely result is that Gmail starts routing a significant portion of that campaign to the Promotions tab or Spam for new recipients who have not previously engaged, meaning the campaign underperforms despite technically high delivery numbers.
Improving email deliverability requires consistent attention to several areas at once. Setting up proper SPF, DKIM, and DMARC authentication for your sending domain is the non-negotiable technical foundation. Beyond that, regularly cleaning your list to remove hard bounces, chronically unengaged addresses, and anyone who has not interacted in over twelve months keeps your engagement signals strong. Segmenting your list to send only the most relevant content to each group further reinforces positive signals. South African businesses using platforms like Klaviyo or Mailchimp should monitor their sender score and inbox placement metrics after every major campaign, not just delivery and open rates, to catch deterioration early.
What actually decides whether mail reaches the inbox
| Factor | Effect |
|---|---|
| Authentication (SPF, DKIM, DMARC) | Baseline requirement; without it, bulk mail is filtered or rejected |
| Sender reputation | Built from complaint rate, bounce rate and engagement over time |
| List quality | Purchased or scraped lists destroy reputation fastest |
| Engagement | Opens, clicks and replies signal wanted mail; sustained silence signals the opposite |
| Complaint rate | The fastest way to be filtered; keep well below industry thresholds |
| Content and links | Matters far less than most people think, but shortened links and mismatched domains hurt |
Authentication is now enforced rather than advisory by major providers for bulk senders. If SPF, DKIM and DMARC are not correctly configured, nothing else on this list will save the campaign.
Diagnosing and fixing a deliverability problem
- Check authentication first. Verify SPF, DKIM and DMARC records actually pass, rather than merely existing.
- Segment by engagement. Stop mailing addresses that have not opened in six months; they suppress reputation for everyone else.
- Clean hard bounces immediately. Repeatedly mailing invalid addresses is a strong negative signal.
- Make unsubscribing easy. An unsubscribe is far less damaging than a spam complaint, and hiding the link converts one into the other.
- Warm new domains and IPs gradually rather than sending to the full list on day one.
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FAQ
What is a good email deliverability rate?
A deliverability rate above 95% is considered healthy for most senders. This means fewer than 5% of your messages are being filtered or blocked. Rates below 90% indicate serious problems with your sender reputation, list quality, or email authentication that need to be addressed before your next campaign.
What is the difference between email delivery and email deliverability?
Email delivery simply means the message was accepted by the recipient's mail server without bouncing. Email deliverability goes further and measures whether the message actually landed in the inbox rather than the spam or junk folder. A message can be delivered but still never be seen if it is routed directly to spam.
Why are my emails going to spam?
Most often authentication is incomplete, the list contains unengaged or purchased addresses, or the complaint rate is high. Verify SPF, DKIM and DMARC pass, suppress addresses that have not engaged in six months, and make unsubscribing obvious.
Do I need DMARC for email marketing?
Yes. Major mailbox providers now enforce authentication for bulk senders, and DMARC alongside SPF and DKIM is the baseline. Without it, delivery becomes unreliable regardless of content quality.