Cold Email Deliverability

What is Cold Email Deliverability?

Cold email deliverability is your ability to land emails in the primary inbox, not spam folders.

It's the multiplier for everything else. Perfect subject lines and brilliant copy don't matter if Gmail sends you to spam.

Deliverability measures two things:

1. Delivery rate: Emails that didn't bounce (technical success)
2. Inbox placement: Emails reaching inbox vs promotions/spam (real success)

Most teams conflate these metrics. Your ESP might show 98% delivery rate while only 62% actually reached inboxes.

That gap between delivery and inbox placement is where deals die.

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Why Deliverability Determines Everything

The math is brutal.

Campaign A: 60% inbox placement × 30% open rate = 18% total opens
Campaign B: 87% inbox placement × 25% open rate = 21.75% total opens

Campaign B generates 21% more opens despite lower open rates. The inbox placement multiplier beats optimization anywhere else.

Industry benchmarks from Mailshake's 2026 study:

• Poor deliverability: <60% inbox placement
• Average deliverability: 60-70% inbox placement
• Good deliverability: 70-85% inbox placement
• Excellent deliverability: 85%+ inbox placement

Firstsales.io averages 87% inbox placement because the entire platform was built around this single metric. Competitors treat deliverability as an afterthought. We made it the foundation.

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The Four Pillars of Deliverability

1. Email Authentication (SPF, DKIM, DMARC)

Authentication proves you're who you claim to be.

SPF (Sender Policy Framework) lists which IP addresses can send from your domain. It's a DNS record saying "only these servers can send email for example.com."

Check: dig TXT example.com and look for v=spf1

DKIM (DomainKeys Identified Mail) adds a cryptographic signature to every email. Receiving servers verify the signature matches your domain.

Check: Your email headers should show dkim=pass

DMARC (Domain-based Message Authentication) tells receiving servers what to do when SPF or DKIM fail.

Options:

• p=none - Monitor only (start here)
• p=quarantine - Send to spam
• p=reject - Bounce the email

Without all three, Gmail and Outlook assume you're suspicious.

Firstsales.io auto-configures SPF, DKIM, and DMARC during setup. No DNS panic required.

2. Domain Reputation

Email providers assign reputation scores to your domain based on behavior.

New domains start at zero reputation. Sending 500 cold emails on day one from a fresh domain triggers every spam filter.

Established domains can still tank reputation through:

• High bounce rates (>5%)
• Spam complaints (>0.1%)
• Low engagement (few opens/clicks)
• Erratic sending patterns

Bounce rate formula:
(Hard bounces + Soft bounces) / Total sent × 100

Keep total bounces under 2%. Above 5% seriously damages sender score.

Spam complaint rate:
Every "mark as spam" click hurts. One complaint per 1,000 emails (0.1%) is the absolute maximum. Lower is better.

Google Postmaster Tools and Microsoft SNDS track your reputation. Check weekly.

3. Gradual Warm-Up

New domains need 21 days minimum to build trust.

Week 1 (Days 1-7):
Send 5-10 emails daily with high engagement. Use internal team emails or warm-up services that guarantee opens and replies.

Week 2 (Days 8-14):
Increase to 15-25 emails daily. Monitor bounce rates obsessively. Any spike above 2% means stop and investigate.

Week 3 (Days 15-21):
Scale to 30-50 emails daily. You're ready for real campaigns.

Week 4+:
Maintain consistent volume. Erratic patterns (500 Monday, 0 Tuesday, 1000 Friday) look like bot behavior.

Manual warm-up is tedious. Firstsales.io automates the entire 21-day process while you focus on messaging.

4. Engagement Quality

Algorithms track how recipients interact with your emails.

High engagement signals:

• ✅ Opens within 2 hours
• ✅ Clicks on links
• ✅ Replies (especially quick ones)
• ✅ Forwarding to colleagues
• ✅ Adding to contacts

Low engagement signals:

• ❌ Deletes without opening
• ❌ Marks as spam
• ❌ No interaction after 24 hours
• ❌ Consistent ignoring

Gmail and Outlook use machine learning to predict if recipients will engage before showing your email. Past behavior predicts future placement.

This is why buying email lists destroys deliverability. Recipients don't know you, don't care, and ignore your emails. The algorithm learns "emails from this domain get ignored" and starts routing to spam.

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Technical Infrastructure

Primary vs Secondary Domains

Never use your primary business domain for cold email.

Primary domain: company.com (for team communication, customer emails, transactional emails)
Secondary domains: outreach.company.com or company.co (for cold outreach only)

If cold email crashes a secondary domain's reputation, your main business communications stay protected.

IP Reputation

Shared IPs pool reputation across all senders using that IP. Dedicated IPs give you complete control but require consistent volume to maintain reputation.

For cold email:

• <10K emails/month → Shared IP (Gmail, Outlook)
• 10K-100K emails/month → Dedicated IP worth considering
• 100K+ emails/month → Dedicated IP required

Firstsales.io uses Google Workspace and Microsoft 365 infrastructure for maximum trust signals.

Email Service Providers

Where you send from matters.

Best for deliverability:

• Gmail (Google Workspace) - Most trusted
• Outlook (Microsoft 365) - Second most trusted
• Custom SMTP on dedicated IP - If you know what you're doing

Avoid for cold email:
- SendGrid, Mailgun, Amazon SES - Built for transactional email, not cold outreach. Different trust signals.

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List Quality Impact

List hygiene directly affects deliverability.

Before every send:

✅ Verify email addresses (remove invalid)
✅ Remove role addresses (info@, hello@, contact@)
✅ Check for spam traps
✅ Remove previous bounces
✅ Remove previous unsubscribes

One spam trap can blacklist your entire domain. Spam traps are email addresses that never belonged to real people, created specifically to catch spammers.

Competitors charge $47/mo extra for list cleaning. Firstsales.io includes it free in all plans because it's not optional.

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Content and Formatting

Content affects deliverability more than most realize.

Spam trigger words to avoid:

• Free, guarantee, act now, limited time
• Buy, purchase, order now
• Click here, click below
• $ $ $ or !!! excessive punctuation

Formatting best practices:

• Plain text often beats HTML for cold email
• No images in initial email (looks like marketing)
• Short paragraphs (2-3 sentences max)
• One clear CTA
• Real signature, not generic

Link hygiene:

• Use custom tracking domains
• Limit to 1-2 links per email
• HTTPS only (never HTTP)
• Avoid URL shorteners (bit.ly looks spammy)

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Monitoring and Recovery

Real-time monitoring catches issues fast.

Track these metrics hourly:

• Inbox placement rate (seed list testing)
• Bounce rate (hard + soft)
• Spam complaint rate
• Open rates by ESP (Gmail vs Outlook)
• Domain reputation scores

Google Postmaster Tools shows:

• Spam rate
• IP reputation
• Domain reputation
• Authentication status

Microsoft SNDS provides:

• IP reputation for Outlook
• Spam trap hits
• Complaint rates

Recovery when deliverability drops:

Step 1: Stop sending immediately
Step 2: Identify the problem (bounces? complaints? content?)
Step 3: Clean list thoroughly
Step 4: Reduce volume 50%
Step 5: Gradually rebuild over 14 days

Prevention beats recovery every time.

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Compliance Requirements

Legal compliance protects deliverability.

CAN-SPAM (United States):

• Clear sender identification
• Accurate subject lines
• Physical mailing address
• Opt-out mechanism (honor within 10 days)

GDPR (European Union):

• Legitimate interest basis for B2B
• Right to be forgotten
• Clear privacy policy
• Record of processing activities

CASL (Canada):

• Express or implied consent
• Implied consent expires after 2 years
• Clear unsubscribe mechanism

Breaking these laws costs money. CAN-SPAM fines reach $51,744 per violation.

More importantly, high spam complaint rates from breaking laws will crater your deliverability permanently.

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Deliverability Checklist

Before launching any campaign:

Technical Setup:

• [ ] SPF record configured
• [ ] DKIM signing enabled
• [ ] DMARC policy set (start with p=none)
• [ ] Custom tracking domain configured
• [ ] Secondary domain for cold email
• [ ] SSL certificate on all linked pages

Domain Health:

• [ ] 21-day warm-up completed
• [ ] Sender reputation score 90+ (Sender Score)
• [ ] Not on any blacklists (check MXToolbox)
• [ ] Google Postmaster Tools green
• [ ] Microsoft SNDS green

List Quality:

• [ ] All addresses verified
• [ ] Bounces removed
• [ ] Unsubscribes removed
• [ ] Role addresses removed
• [ ] Spam traps checked

Content:

• [ ] Plain text format
• [ ] No spam trigger words
• [ ] HTTPS links only
• [ ] Custom tracking domain
• [ ] One clear CTA
• [ ] Real signature with title

Monitoring:

• [ ] Seed list testing setup
• [ ] Bounce rate alerts configured
• [ ] Spam complaint tracking
• [ ] Daily deliverability reports

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Related Terms

• Domain Warm-Up - Building sender reputation gradually
• Sender Reputation - How ESPs view your domain
• SPF - Email authentication protocol
• DKIM - Cryptographic email signing
• DMARC - Authentication policy framework

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Next: Read our complete 23-step cold email deliverability checklist to never land in spam again.