Practical Guide to Sending Cold Emails That Avoid Spam Filters and Deliverability Issues
A comprehensive guide covering email infrastructure setup, domain reputation management, message structure optimization, sending volume best practices, and compliance requirements to ensure your cold outreach actually reaches the inbox.
Why Cold Emails Land in Spam
Technical Issues
Email providers use authentication protocols to verify sender legitimacy. Missing or misconfigured records instantly flag your emails as suspicious.
- No SPF record: Cannot verify sending server authorization
- Missing DKIM: Cannot verify email was not altered in transit
- No DMARC policy: No instructions for handling failed authentication
- New domain: No sending history equals no trust
The Cold Email Problem
Cold emails face extra scrutiny because:
- Recipients did not subscribe or opt-in
- Similar emails often get marked as spam by others
- High volume from new domains raises red flags
- Generic content triggers spam filters
Content Issues
Even with perfect technical setup, certain content patterns trigger spam filters and reduce deliverability.
- Spam trigger words: "Free," "Act now," "Limited time," "Guaranteed"
- Excessive formatting: ALL CAPS, too many exclamation marks!!!
- Too many links: Multiple URLs or link shorteners
- Image-heavy: Low text-to-image ratio
Behavioral Issues
How recipients interact with your emails impacts future deliverability. Negative signals compound over time.
- Low open rates: Signal that emails are unwanted
- High unsubscribe rates: Indicate irrelevant targeting
- Spam complaints: Even 0.1% rate causes issues
- Bounces: High bounce rates damage sender reputation
Email Infrastructure Setup: The Foundation
SPF (Sender Policy Framework)
SPF tells receiving servers which mail servers are authorized to send email on behalf of your domain.
v=spf1 include:_spf.google.com ~all
- Add as TXT record in DNS
- Include all sending services
- Use ~all (soft fail) initially
DKIM (DomainKeys Identified Mail)
DKIM adds a digital signature to emails, allowing recipients to verify the email was not modified in transit.
selector._domainkey.domain.com
- Generated by email provider
- Add public key to DNS
- Unique per sending service
DMARC (Domain-based Message Authentication)
DMARC tells receiving servers what to do with emails that fail SPF or DKIM checks.
v=DMARC1; p=none; rua=mailto:[email protected]
- Start with p=none (monitor)
- Set up reporting address
- Gradually increase to p=quarantine
Setup Checklist for Cold Email Infrastructure
Domain Setup
- Use a separate domain for cold outreach
- Choose a domain similar to your main brand
- Configure SPF, DKIM, and DMARC records
- Set up a basic website on the domain
Email Account Setup
- Use Google Workspace or Microsoft 365
- Create 2-3 email accounts per domain
- Add profile photo and signature
- Enable 2FA for account security
Why Use a Separate Domain?
Never use your main business domain for cold outreach. If your cold emails get flagged as spam, it can damage your main domain's reputation and affect transactional emails to existing customers.
Good Example
- Main domain: acmedesign.com
- Outreach domain: acme-design.com
- Or: getacmedesign.com
Bad Practice
- Using random unrelated domain
- Using free email providers
- Using your main transactional domain
Domain Warming: Building Trust Over Time
What Is Domain Warming?
New domains have no sending reputation. Email providers treat them with suspicion. Warming gradually builds positive sending history before scaling up volume.
Start Very Small
Begin with 10-20 emails per day to real addresses you know will engage.
Increase Gradually
Add 10-20% more volume each week. Never jump from 20 to 200.
Generate Positive Signals
Ensure recipients open, reply, and do not mark as spam.
Monitor Metrics
Track deliverability, open rates, and bounce rates throughout.
Warming Timeline Example
A typical 4-week warming schedule before starting cold outreach campaigns:
| Week | Daily Volume | Activity |
|---|---|---|
| Week 1 | 10-20 | Personal emails to known contacts |
| Week 2 | 25-40 | Mix of personal and warm leads |
| Week 3 | 50-75 | Begin introducing cold emails |
| Week 4 | 75-100 | Mostly cold with some warm |
| Week 5+ | 100-150 | Full cold outreach (stable) |
* Volume limits are per email account. Multiple accounts can increase total daily sends.
Automated Warming Services
Dedicated warming tools automate the process by sending and receiving emails with other warming network accounts:
- Instantly.ai, Warmbox, Mailwarm, Lemwarm
- Simulate real conversations automatically
- Remove from spam, mark as important
- Typically $30-100/month per mailbox
Common Warming Mistakes
- Rushing the process: Jumping to high volume too quickly destroys new reputation.
- Only warming, no real emails: Mix warming with legitimate conversations.
- Stopping too early: Continue warming even after starting campaigns.
- Ignoring metrics: Not monitoring deliverability during warm-up.
Email Content That Avoids Spam Triggers
Spam Trigger Words to Avoid
Certain words and phrases significantly increase spam filter scores. Use alternatives or context carefully.
High-Risk Words
Medium-Risk Words
Subject Line Best Practices
Your subject line is the first thing spam filters analyze. Keep it natural and relevant.
Do This
- - "Quick question about [Company Name]"
- - "[First Name] - [specific topic]"
- - "Following up on [topic]"
- - "Idea for [specific problem]"
Avoid This
- - "FREE Website Audit!!!"
- - "LIMITED TIME OFFER"
- - "You Won't Believe This Deal"
- - "Re: Re: Fwd: Important"
Email Body Structure for Deliverability
Formatting Rules
- Keep emails short (50-150 words ideal)
- Use plain text format (no heavy HTML)
- Maximum 1-2 links per email
- No images in cold emails
- Include a real email signature
- Use full URLs, avoid link shorteners
Things to Avoid
- ALL CAPS anywhere in the email
- Multiple exclamation marks!!!
- Colored or oversized fonts
- Attachments (especially first email)
- Too many merge tags (looks templated)
- Bit.ly, goo.gl, or other shorteners
Example Cold Email Template (Deliverability Optimized)
Subject: Quick question about [Company Name]
Hi [First Name],
I noticed [specific observation about their business]. [One sentence about why you are reaching out].
[One sentence about what you do and the value you provide - no hype].
Would you be open to a quick call this week to see if this could help [Company Name]?
Best,
[Your Name]
[Your Title] | [Your Company]
[Phone Number]
Notice: No spam trigger words, single question CTA, personalized opening, plain text format, professional signature.
Sending Volume and Timing Best Practices
Volume Limits Per Account
Sending too many emails from a single account is the fastest way to damage reputation. Follow these guidelines:
New Accounts (0-4 weeks)
Daily limit
20-50
Weekly limit
100-250
Warmed Accounts (1-3 months)
Daily limit
50-100
Weekly limit
250-500
Mature Accounts (3+ months)
Daily limit
100-150
Weekly limit
500-750
* These limits include all emails - both cold outreach and replies. Google Workspace and Microsoft 365 have technical limits around 500/day, but reputation limits are much lower.
Optimal Sending Times
When you send matters almost as much as what you send. Timing affects both deliverability and open rates.
Best Days
Tuesday, Wednesday, Thursday - highest open rates and engagement.
Best Times
Send in the recipient's timezone:
- - 8:00-10:00 AM (morning check)
- - 1:00-3:00 PM (post-lunch lull)
Avoid
- - Mondays (inbox overload)
- - Fridays after 2pm (weekend mode)
- - Weekends (low engagement)
- - After 6pm (personal time)
Sending Patterns That Look Natural
Space Out Sends
Add random delays of 60-180 seconds between emails. Avoid sending 50 emails in 5 minutes.
Vary Your Schedule
Do not send at exactly the same time every day. Vary by 30-60 minutes to appear human.
Use Multiple Accounts
Spread volume across 3-5 email accounts rather than pushing one to its limits.
List Hygiene: The Foundation of Deliverability
Why Bounces Destroy Deliverability
High bounce rates signal to email providers that you are sending to bad lists, a hallmark of spammers.
Bounce Rate Thresholds
Even a single campaign with high bounces can damage your sending reputation for weeks.
Email Verification Best Practices
Always verify email addresses before sending. Verification services catch invalid emails before they bounce.
- Verify every email: Use services like NeverBounce, ZeroBounce, or Clearout
- Remove catch-all domains: These accept all emails but may not deliver
- Re-verify old lists: Email validity decays 2-3% per month
- Check for spam traps: Some services detect known trap addresses
List Quality Checklist Before Sending
Data Quality
- All emails verified within last 30 days
- Bounce rate under 2% in previous campaigns
- Role-based emails removed (info@, sales@)
- Duplicate entries removed
Targeting Quality
- Contacts match your ICP (ideal customer profile)
- Company data is current and accurate
- Contact has relevant job title/role
- Unsubscribes from previous campaigns excluded
Compliance: Legal Requirements for Cold Email
CAN-SPAM (United States)
The CAN-SPAM Act governs commercial email in the US. Violations can result in penalties up to $50,000 per email.
Your name and company must be identifiable
Include a valid postal address in every email
Provide a clear way to opt out of future emails
Remove unsubscribed contacts promptly
Subject must accurately reflect content
GDPR (European Union)
GDPR has stricter requirements. B2B cold email is possible under "legitimate interest" but requires careful handling.
Document why recipient would reasonably expect contact
Link to privacy policy explaining data use
Delete data upon request within 30 days
B2B only, and genuinely relevant to their role
Note: GDPR applies when emailing anyone in the EU, regardless of where you are located.
Practical Compliance for Cold Email
Always Include
- Your real name and company name
- Physical mailing address in signature
- Easy unsubscribe option (link or reply instruction)
- Relevant, truthful subject line
Best Practices
- Honor opt-outs immediately, not just within 10 days
- Keep records of where you obtained contact data
- Maintain a suppression list across all campaigns
- Review and update compliance practices regularly
Monitoring and Troubleshooting Deliverability
Key Metrics to Track
Percentage of emails that reach recipient servers (not bounced)
Percentage landing in inbox vs spam folder (harder to track)
Healthy open rates suggest good deliverability
Hard bounces damage reputation immediately
Even low rates cause significant problems
Monitoring Tools
Free Tools
- Google Postmaster Tools: Monitor Gmail deliverability
- MXToolbox: Check DNS records and blacklists
- Mail-tester.com: Test email spam score
Paid Tools
- GlockApps: Inbox placement testing
- Mailgun: Analytics and deliverability metrics
- SendForensics: Reputation monitoring
When Deliverability Drops: Troubleshooting Checklist
Immediate Actions
- Pause all campaigns immediately
- Check if domain is on any blacklists
- Verify SPF, DKIM, DMARC still configured
- Review recent email content for spam triggers
Recovery Steps
- Request removal from any blacklists
- Reduce volume to 20% of previous levels
- Re-warm domain over 2-4 weeks
- Consider using a new domain if severely damaged
Key Takeaways
Technical Setup Is Non-Negotiable
SPF, DKIM, and DMARC must be properly configured before sending any cold emails. Missing authentication is an instant spam trigger.
Warming Takes Time - Do Not Skip It
Plan for 2-4 weeks of warming before launching cold campaigns. Patience now prevents destroyed reputation later.
Content Matters as Much as Infrastructure
Write like a human, avoid spam triggers, keep emails short, and limit links. The best technical setup will not save bad content.
Volume Limits Exist for Good Reason
50-150 emails per day per account is the safe zone. Use multiple accounts to scale, not higher per-account volume.
List Quality Determines Success
Always verify emails before sending. High bounce rates destroy reputation faster than any other factor.
Monitor Continuously, Fix Quickly
Track delivery rates, open rates, and bounces. When metrics drop, pause and troubleshoot immediately before damage compounds.
Ready to Build Your Cold Outreach System?
RangeLead provides verified B2B lead data for local businesses across the United States. Start with clean, verified contacts to maximize your deliverability from day one.