Email Deliverability

What is Email Deliverability?

Email deliverability is the set of practices and metrics that determine whether your messages reach the recipient's inbox rather than being rejected, filtered to spam, or silently dropped. It sits at the intersection of infrastructure, authentication, content, and list hygiene.

Why it matters

You can build the best product and write the most compelling copy, but if your mail lands in spam none of it matters. Deliverability affects activation, revenue, and retention directly. Founders, marketers, and platform engineers all share responsibility, and the cost of ignoring it compounds silently until a reputation crisis forces the issue.

How it works

Mailbox providers evaluate every inbound message against dozens of signals: authentication results from SPF, DKIM, and DMARC, the sending IP's historical reputation, domain reputation, content cues, recipient engagement, complaint rate, and the consistency of your sending volume. These signals feed an internal score that decides whether the message goes to inbox, promotions, spam, or nowhere. Because the rules are proprietary and change often, deliverability is an ongoing discipline rather than a one-time setup.

Examples

• A team that fixed DMARC alignment and saw inbox placement jump from 78 to 96 percent
• A startup whose Monday blast tanked reputation because it spiked volume 10x the daily average
• A marketer using seed lists across providers to monitor placement rate week over week

Best practices

• Authenticate with SPF, DKIM, and DMARC before sending any production traffic
• Warm up new IPs and domains slowly to establish a volume pattern
• Segment out disengaged recipients to protect reputation
• Use a deliverability-aware provider like Sendkit that monitors reputation for you

FAQs

What is a good inbox placement rate?

Above 95 percent is excellent for marketing, above 98 percent is realistic for transactional. Below 90 percent means you have problems to investigate.

How is deliverability different from delivery rate?

Delivery rate only measures whether the receiving server accepted the message. Deliverability goes further and asks whether it reached the actual inbox, not the spam folder.

Can a single bad campaign ruin my deliverability?

Yes, if the campaign generates a large spike in complaints, spam traps, or bounces. Reputation takes weeks to build and hours to damage.