Email Deliverability Guide: How to Land in the Inbox

What is Email Deliverability?

Email deliverability is the ability to get your emails into recipients' inboxes — not spam folders. Even if your email is "delivered" (accepted by the mail server), it may still end up in spam.

Key metrics:

• Delivery rate: % of emails accepted by mail servers (should be >98%)
• Inbox placement rate: % of delivered emails that reach the inbox (should be >90%)
• Bounce rate: % of emails rejected by mail servers (should be <2%)
• Spam complaint rate: % of recipients marking you as spam (should be <0.1%)

Authentication: The Foundation

SPF (Sender Policy Framework)

SPF tells receiving servers which IPs are authorized to send email for your domain.

# DNS TXT record for yourdomain.com
v=spf1 include:_spf.unosend.co ip4:217.217.250.114 ip6:2400:d321:2294:2881::1 ~all

DKIM (DomainKeys Identified Mail)

DKIM adds a cryptographic signature to every email, proving it wasn't tampered with in transit.

# DNS TXT record for unosend._domainkey.yourdomain.com
v=DKIM1; k=rsa; p=MIIBIjANBg...

DMARC (Domain-based Message Authentication)

DMARC ties SPF and DKIM together and tells servers what to do with failed emails.

# DNS TXT record for _dmarc.yourdomain.com
v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com

Start with p=none to monitor, then move to p=quarantine and finally p=reject.

Sender Reputation

Your sender reputation is like a credit score for email. ISPs (Gmail, Outlook, Yahoo) track:

• Bounce rates — High bounces indicate bad list hygiene
• Spam complaints — Each complaint significantly hurts reputation
• Engagement — Opens and clicks boost reputation
• Sending volume — Sudden spikes look suspicious

How to Build Reputation

• Start slow — Don't send 100K emails on day one
• Warm up your IP — Gradually increase volume over 2-4 weeks
• Clean your list — Remove invalid emails before sending
• Monitor bounces — Automatically suppress bounced addresses
• Make unsubscribing easy — A visible unsubscribe link reduces spam complaints

Content Best Practices

• Avoid spam trigger words — "FREE", "Act now", "Limited time" in excess
• Balance text and images — Don't send image-only emails
• Include a plain text version — Always provide a text fallback
• Use a consistent From name — Recipients should recognize you
• Personalize — Personalized subject lines improve open rates by 26%

Monitoring & Tools

• Google Postmaster Tools — See your domain reputation with Gmail
• Microsoft SNDS — Monitor your reputation with Outlook/Hotmail
• Mail-Tester.com — Test your email for spam score before sending
• Unosend Dashboard — Track delivery, opens, clicks, and bounces in real-time

Quick Checklist

• SPF record configured
• DKIM record configured
• DMARC record set to at least `p=none`
• Dedicated sending domain (not personal email)
• Clean email list (validated addresses)
• Easy unsubscribe link in every email
• Monitoring bounces and complaints
• Consistent sending volume (no sudden spikes)