Email Deliverability Best Practices

Email deliverability is the ability to successfully deliver emails to recipients' inboxes rather than spam folders. Good deliverability requires attention to technical setup, list quality, content, and sender reputation.

Email Authentication

Proper authentication is the foundation of good deliverability. You need all three:

SPF (Sender Policy Framework)

Authorizes which IP addresses can send email for your domain.

example.com.  TXT  "v=spf1 include:_spf.google.com ~all"

DKIM (DomainKeys Identified Mail)

Cryptographically signs your emails to prove authenticity.

selector._domainkey.example.com.  TXT  "v=DKIM1; k=rsa; p=..."

DMARC (Domain-based Message Authentication)

Tells receivers what to do when SPF/DKIM fail and provides reporting.

_dmarc.example.com.  TXT  "v=DMARC1; p=reject; rua=mailto:dmarc@example.com"

Infrastructure Setup

Dedicated Sending IP

For high-volume senders, use a dedicated IP address. This isolates your reputation from other senders on shared infrastructure.

Reverse DNS (PTR Record)

Your mail server's IP should have a PTR record that matches your sending hostname:

# Your mail server sends as: mail.example.com
# PTR record should resolve to: mail.example.com
# The A record for mail.example.com should point back to the IP

Warm Up New IPs

New IP addresses have no reputation. Gradually increase sending volume:

Week	Daily Volume
1	50-100
2	200-500
3	1,000-2,000
4	5,000-10,000
5+	Gradually increase to target

TLS Encryption

Enable opportunistic TLS for encrypted transmission. Most modern mail servers support this.

List Hygiene

Use Double Opt-In

Require subscribers to confirm their email address before adding them to your list. This ensures valid addresses and engaged subscribers.

Remove Bounces Immediately

• Hard bounces — Remove immediately (invalid address)
• Soft bounces — Remove after 3-5 consecutive failures

Honor Unsubscribes Promptly

Process unsubscribe requests within 24 hours. Include a visible one-click unsubscribe link and support the List-Unsubscribe header:

List-Unsubscribe: <mailto:unsubscribe@example.com>, <https://example.com/unsubscribe>
List-Unsubscribe-Post: List-Unsubscribe=One-Click

Re-Engage or Remove Inactive

Subscribers who haven't opened or clicked in 6-12 months hurt your metrics:

1. Send a re-engagement campaign
2. Give them a reason to stay
3. Remove those who don't respond

Content Best Practices

Subject Lines

• Avoid ALL CAPS and excessive punctuation!!!
• Don't use spam trigger words excessively (free, guarantee, act now)
• Be honest — misleading subjects increase complaints
• Keep it relevant to the email content

Email Body

• Balance text and images — Don't send image-only emails
• Include plain text version — Multipart emails are better received
• Use a consistent From name/address — Helps recipients recognize you
• Include your physical address — Required by CAN-SPAM

Links

• Don't use URL shorteners — they're associated with spam
• Ensure all links work and point to legitimate sites
• Avoid linking to newly registered domains

Monitoring & Metrics

Key Metrics to Track

Metric	Good	Concerning
Bounce Rate	< 2%	> 5%
Complaint Rate	< 0.1%	> 0.3%
Unsubscribe Rate	< 0.5%	> 1%
Open Rate	> 20%	< 10%

Set Up Feedback Loops

Register with major ISPs to receive notifications when recipients mark your email as spam. Immediately remove complainers from your list.

Use Postmaster Tools

• Google Postmaster Tools — Monitor Gmail delivery and reputation
• Microsoft SNDS — Monitor Outlook/Hotmail delivery
• Yahoo Postmaster — Monitor Yahoo Mail delivery

Monitor Blacklists

Regularly check if your sending IPs or domains are blacklisted. Catching a listing early allows faster remediation.