The Complete Guide to Email Deliverability in 2026

Email deliverability is the measure of how successfully your emails reach recipients' inboxes. Poor deliverability means wasted effort and frustrated users. Here's how to get it right.

Authentication Matters

Modern email authentication relies on three key protocols:

SPF (Sender Policy Framework)

SPF specifies which servers can send email on behalf of your domain. Add this to your DNS:

v=spf1 include:_spf.postscale.io ~all

DKIM (DomainKeys Identified Mail)

DKIM adds a cryptographic signature to your emails. Postscale automatically signs all outgoing emails with your domain's DKIM key.

DMARC (Domain-based Message Authentication)

DMARC tells receiving servers what to do with emails that fail SPF/DKIM checks:

v=DMARC1; p=quarantine; rua=mailto:dmarc@yourapp.com

Content Best Practices

Do:

• Use a recognizable "From" name
• Write clear, relevant subject lines
• Include a plain text version
• Make unsubscribe easy to find

Don't:

• Use ALL CAPS in subject lines
• Include too many images
• Use URL shorteners
• Send from a no-reply address

Warming Up New Domains

When you start sending from a new domain, gradually increase volume:

Monitor Your Reputation

Keep an eye on:

• Bounce rates (should be under 2%)
• Spam complaints (should be under 0.1%)
• Blacklist status (check regularly)

Postscale's dashboard shows all these metrics in real-time, so you can catch problems early.