What Is Email Deliverability?

The ability of an email to reach the recipient's inbox rather than their spam folder or being rejected entirely by the mail server.

Email deliverability is the percentage of sent emails that successfully reach the recipient's inbox — as opposed to being routed to the spam folder, soft-bouncing (temporary failure), or hard-bouncing (permanent rejection). High deliverability is the foundation of any cold email campaign; without it, the quality of your message and targeting is irrelevant.

What receiving mail servers check

1. Authentication: Does the email pass SPF, DKIM, and DMARC checks? Failed authentication is an immediate spam signal.
2. Sender reputation: What is the historical reputation of this sending domain and IP? Blacklisted or low-reputation senders go to spam.
3. Content signals: Does the email contain spam trigger words, suspicious links, or deceptive headers?
4. Engagement history: Do recipients from this domain typically open and reply, or do they mark as spam?
5. Volume patterns: Is the sending volume consistent with the domain's history, or does it represent an unusual spike?

Key deliverability metrics

• Inbox placement rate: % of delivered emails that reach the inbox (vs. spam folder)
• Bounce rate: % of sent emails that are returned (hard or soft). Keep below 2%.
• Spam complaint rate: % of recipients who mark your email as spam. Google requires below 0.10%.
• Open rate: Used as a proxy for inbox placement, though less reliable due to Apple Mail Privacy Protection

How to measure your deliverability

Google Postmaster Tools (free) shows spam rate and domain reputation for Gmail recipients. Mail-tester.com gives a deliverability score (1–10) by analysing a test email. MXToolbox checks authentication records and blacklists.

Related terms

Put Email Deliverability into practice with YOG.io

YOG.io is a governed outbound platform — AI discovers verified contacts, AI drafts personalised sequences, and a human approves before every send.