The Email Deliverability Checklist: Stop Landing in Spam

Here's a scenario we see constantly: A company launches an outbound email campaign. They've written great copy. They've built a solid target list. They've set up sequences in their sales engagement tool. And nothing happens. Open rates are below 20%. Reply rates are near zero.

They blame the messaging. They rewrite the emails. Still nothing. They blame the list. They buy new data. Still nothing.

The problem isn't the message or the list. The problem is deliverability. Their emails are landing in spam, promotions tabs, or getting silently rejected, and they have no idea.

The Technical Foundation

1. Domain Setup

Never send outbound from your primary domain. If your company is acme.com, your outbound emails should come from a separate domain like acmemail.com or getacme.com.

Why? If your outbound domain gets flagged for spam, it doesn't drag down your primary domain's reputation. Your marketing emails, transactional emails, and employee communications stay safe.

Setup checklist:

• Buy 2-3 secondary domains for outbound
• Set up Google Workspace or Microsoft 365 on each domain
• Create individual mailboxes (not aliases) for each sender
• Set up a simple website on each domain (even a one-page site), naked domains look suspicious

2. Authentication Records

These are non-negotiable. If any of these are missing, you're starting with a handicap.

SPF (Sender Policy Framework):

• Add a TXT record to your DNS that specifies which servers can send email on your behalf
• Include your email provider and any sending tools (Outreach, Apollo, etc.)
• Check with: mxtoolbox.com/spf.aspx

DKIM (DomainKeys Identified Mail):

• A cryptographic signature that proves the email wasn't tampered with in transit
• Usually set up through your email provider, they give you a TXT record to add to DNS
• Check with: mail-tester.com

DMARC (Domain-based Message Authentication):

• Tells receiving servers what to do when SPF or DKIM fails
• Start with a monitoring policy: v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com
• Graduate to quarantine or reject once you're confident
• Check with: dmarcian.com

3. Domain Warming

New domains have no reputation. Sending 100 emails on day one from a fresh domain is a guaranteed spam flag.

The warming schedule:

• Week 1-2: Send 5-10 personal emails per day to known contacts who will reply. Gmail and Outlook track reply rates, getting replies builds reputation.
• Week 3-4: Increase to 15-25 emails per day. Mix personal and semi-automated.
• Week 5-6: Increase to 30-50 emails per day. Begin light outbound.
• Week 7+: Scale to your target volume (usually 50-80 per mailbox per day max).

Or use a warming tool: Mailreach, Warmbox, or Instantly's built-in warmer. These send automated emails between real inboxes to build reputation. Run warming for at least 2 weeks before any outbound, and keep it running alongside your campaigns.

The Behavioural Layer

Technical setup gets you to the inbox. Behavioural signals keep you there.

4. Sending Volume and Patterns

Daily limits per mailbox:

• Google Workspace: Max 50-80 cold emails per day
• Microsoft 365: Max 50-80 cold emails per day
• Never exceed 100 total sends (including warmup) per mailbox per day

Sending patterns:

• Spread sends across the day (not 50 emails at 9:01 AM)
• Use human-like intervals (randomise by 30-90 seconds between sends)
• Don't send on weekends (low engagement tanks your metrics)
• Reduce volume on Mondays and Fridays

5. Content Best Practices

Spam filters read your emails. Write like a human, not a marketer.

Do:

• Write in plain text (no HTML templates for cold email)
• Keep emails under 150 words
• Use 1-2 links maximum (and never in email 1)
• Write lowercase subject lines
• Include a clear unsubscribe option
• Use your real name and title in the signature

Don't:

• Use spam trigger words: "free," "guarantee," "act now," "limited time"
• Include images or attachments in cold emails
• Use URL shorteners (bit.ly links are spam signals)
• Use tracking pixels in every email (reduce to every other email)
• CC or BCC multiple recipients
• Use exclamation marks in subject lines

6. List Hygiene

Bad data kills deliverability faster than anything else.

• Verify every email before sending. Use NeverBounce, ZeroBounce, or Debounce.
• Remove catch-all domains: They accept every email but often don't deliver internally. They also don't bounce, so you never know your emails are going to a dead inbox.
• Remove role-based addresses: info@, sales@, team@ addresses rarely reach individuals.
• Deduplicate across sequences: Sending the same person two different sequences is a fast track to spam reports.
• Honour unsubscribes immediately: Even before legal compliance, each spam report damages your sender reputation.

The Monitoring Layer

7. Track the Right Metrics

Your sales engagement tool shows open and reply rates. But for deliverability, you need more:

• Inbox placement rate: What percentage of emails land in the primary inbox vs. spam vs. promotions? Use GlockApps or MailReach monitoring.
• Bounce rate: Keep below 3%. Above 5% indicates list quality issues.
• Spam complaint rate: Keep below 0.1%. Above 0.3% and you're in danger.
• Domain health score: Check Google Postmaster Tools (if sending to Gmail) and Microsoft SNDS (if sending to Outlook).

8. The Weekly Deliverability Audit

Every Friday, spend 15 minutes:

1. Check inbox placement rates across all sending domains
2. Review bounce rates by domain and list source
3. Check Google Postmaster Tools for reputation changes
4. Review any spam complaints and identify patterns
5. Verify warming tools are still running
6. Check sending volumes against limits

If any metric degrades, pause outbound from that domain immediately and diagnose.

The Recovery Playbook

Already in spam? Here's how to recover:

Mild Damage (Open rates dropped 10-20%)

• Reduce sending volume by 50% for 2 weeks
• Increase warming volume
• Remove disengaged contacts from sequences
• Review and clean your content
• Re-check authentication records

Moderate Damage (Open rates below 30%)

• Pause all outbound from affected domain for 1 week
• Run warming only for 2 weeks
• Rebuild lists with fresh, verified data
• Rewrite all email content
• Resume at 25% of previous volume

Severe Damage (Domain blacklisted)

• Check blacklist status at mxtoolbox.com/blacklists.aspx
• Submit delisting requests to each blacklist
• Pause the domain for 30 days
• Consider retiring the domain and warming a new one
• Investigate root cause before restarting

The Bottom Line

Email deliverability is not a set-it-and-forget-it problem. It's an ongoing practice that requires technical setup, behavioural discipline, and continuous monitoring.

The best cold email in the world is worthless if it lands in spam. Fix your deliverability first, then worry about your copy.

Print this checklist. Run through it quarterly. Your pipeline depends on it.