Email Deliverability Best Practices for Cold Outreach

Getting your cold emails to actually reach the inbox is harder than ever. ISPs are increasingly sophisticated at filtering out bulk senders, and one mistake can tank your sender reputation for months.

This guide covers the essential strategies we've learned from helping hundreds of teams maintain 95%+ inbox placement rates.

Understanding Deliverability

Deliverability is whether your email reaches the inbox, spam folder, or gets blocked entirely. It's determined by:

• Sender reputation (domain and IP)
• Authentication (SPF, DKIM, DMARC)
• Engagement signals (opens, clicks, replies)
• Content quality and spam triggers
• Recipient behavior (complaints, deletes without reading)

The Deliverability Spectrum

Emails don't just go to "inbox" or "spam." The reality is more nuanced:

1. Primary inbox - Best case, visible immediately
2. Promotions/Updates tab - Gmail's filtered inboxes
3. Spam folder - Bad, but recoverable
4. Blocked entirely - Worst case, no delivery at all

Your goal is consistent primary inbox placement.

Technical Setup: Get This Right First

Before sending a single email, ensure your technical foundation is solid.

Domain Authentication

Configure these DNS records for your sending domain:

SPF Record - Specifies which servers can send from your domain

v=spf1 include:_spf.google.com ~all

DKIM Record - Cryptographically signs your emails

(Generated by your email provider)

DMARC Record - Tells ISPs how to handle authentication failures

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

Use MXToolbox to verify your setup.

Separate Domains for Different Use Cases

Consider using different domains for:

5. Transactional email (app.mailsequence.com → no-reply@mail.mailsequence.com)
6. Marketing campaigns (newsletter@mailsequence.com)
7. Cold outreach (team members @mailsequence.com)

This isolates reputation. If cold outreach hurts reputation, it won't affect your transactional email deliverability.

Volume Strategy: Less Is More

The biggest mistake: sending too much, too fast.

Recommended Daily Limits

Per inbox, per day:

8. New domain/inbox: Start at 10-20 emails/day
9. After 2 weeks warmup: 30-50 emails/day
10. After 4 weeks warmup: 50-75 emails/day
11. Established inbox: Max 100 emails/day

These are conservative limits that maintain reputation. Some sources recommend higher, but we've seen better long-term results staying conservative.

The Power of Rotation

Instead of sending 500 emails from one inbox, send 75 emails from 7 inboxes.

Benefits:

12. Each inbox stays under daily limits
13. Reputation risk is distributed
14. If one inbox has issues, others continue working
15. You can scale by adding inboxes, not increasing risk per inbox

This is why MailSequence emphasizes inbox rotation as a core feature.

Content That Avoids Spam Filters

Even with perfect technical setup, poor content triggers spam filters.

Spam Trigger Words to Avoid

Minimize use of:

16. Financial terms: "free money," "earn $$$," "investment opportunity"
17. Urgency: "act now," "limited time," "urgent response needed"
18. Exaggeration: "amazing," "incredible," "revolutionary"
19. Suspicious phrases: "click here," "dear friend," "this is not spam"

Content Best Practices

Do:

20. Write like a human, not a marketer
21. Keep it concise (under 200 words is ideal)
22. Personalize beyond just first name
23. Have a clear, single call-to-action
24. Use plain text or minimal HTML
25. Include a professional signature

Don't:

26. Use all caps or excessive punctuation!!!
27. Insert too many links (1-2 max)
28. Use link shorteners (bit.ly, etc.)
29. Include attachments in first email
30. Use bright colors or large fonts
31. Send image-only emails

The Plain Text Advantage

Consider sending plain text emails instead of HTML. They:

32. Look more personal and less "marketing-y"
33. Avoid HTML rendering issues
34. Have fewer spam triggers
35. Load faster on mobile

Most top-performing cold email is plain text with simple formatting.

Engagement: The Ultimate Signal

ISPs track how recipients interact with your emails. High engagement = good sender.

Engagement Metrics That Matter

Positive signals:

36. Opens (but note: tracking is imperfect post-iOS 15)
37. Clicks
38. Replies (strongest signal)
39. Moving from spam to inbox
40. Starring/flagging
41. Adding sender to contacts

Negative signals:

42. Deleting without reading
43. Marking as spam (very bad)
44. Low open rates over time
45. Bounces

How to Boost Engagement

Target the right people:

46. Send to people who might actually be interested
47. Segment your list carefully
48. Use qualification criteria before adding to sequences

Write compelling subject lines:

49. Short (under 50 characters)
50. Personal, not promotional
51. Question or curiosity-driven
52. Test variations with A/B testing

Make replies easy:

53. Ask a simple question
54. Use the "PAS" framework: Problem, Agitation, Solution
55. End with a soft CTA (not "book a meeting," try "worth a quick chat?")

The Reply Rate Rule

Aim for at least 2-5% reply rate on cold sequences. If you're below that consistently, fix your targeting or messaging before sending more volume.

Warmup: Building Reputation Gradually

Never go from 0 to 100 emails per day. ISPs need to see gradual, organic growth.

Warmup Schedule (4 Weeks)

Week 1: 10 emails/day Week 2: 20 emails/day Week 3: 40 emails/day Week 4: 60 emails/day Week 5+: 75-100 emails/day (monitor closely)

During warmup:

56. Send to engaged recipients (past customers, opted-in contacts)
57. Aim for high reply rates
58. Avoid spam triggers
59. Monitor reputation daily

MailSequence automates this warmup process, but you can do it manually if needed.

Monitoring and Maintenance

Deliverability isn't "set and forget." Monitor continuously.

Key Metrics to Track

Daily:

60. Bounce rate (keep under 2%)
61. Spam complaint rate (keep under 0.1%)
62. Reply rate (aim for 2-5%+)

Weekly:

63. Sender reputation score (Google Postmaster Tools, Microsoft SNDS)
64. Open rate trends
65. Unsubscribe rate

Monthly:

66. Domain reputation via third-party tools
67. Deliverability tests (send to seed lists)
68. Review content performance

When to Pause

Stop sending if you see:

69. Bounce rate above 5%
70. Spam complaint rate above 0.3%
71. Sender reputation score drops to "Poor" or "Bad"
72. Sudden drop in open rates (>50% decline)

Diagnose the issue, fix it, then resume with reduced volume.

Recovery: What to Do When Things Go Wrong

Sender reputation damage happens. Here's how to recover:

Step 1: Identify the Issue

Common causes:

73. Purchased or scraped email lists (never do this)
74. Sending too much, too fast
75. Poor targeting (sending to uninterested people)
76. Content triggering spam filters
77. Technical misconfiguration

Step 2: Fix the Root Cause

78. Review and clean your contact list
79. Improve targeting criteria
80. Rewrite sequences to remove spam triggers
81. Verify DNS records are correct
82. Reduce volume significantly

Step 3: Rebuild Reputation

83. Drop volume to 10-20 emails/day
84. Send only to highly engaged segments
85. Monitor metrics obsessively
86. Gradually increase only when metrics improve
87. Consider using a new subdomain if reputation is severely damaged

Recovery can take 2-6 weeks. Patience is critical.

Advanced Strategies

Once you've mastered the basics:

Custom Tracking Domains

Use a separate subdomain for link tracking:

88. Instead of: click.mailsequence.com/track/abc123
89. Use: track.yourdomain.com/abc123

This keeps your main domain reputation clean and gives you control over tracking infrastructure.

Inbox Warm-Up Services

Services like Mailwarm and Lemwarm automate warm-up by sending emails to other warm-up users who engage with them.

Pros: Automates engagement signals Cons: Artificial engagement, costs extra, ISPs may detect patterns

We recommend natural warm-up when possible, but these services can help for new domains.

Per-Contact Sending Limits

Set daily limits per inbox, but also consider:

90. Max 1 email per contact per week
91. Stop after 3-4 touches with no reply
92. Longer delays between follow-ups (3-5 days, not 1-2 days)

This shows ISPs you respect recipients and aren't "spamming" the same people repeatedly.

Conclusion

Deliverability comes down to three things:

93. Technical foundation - DNS records, authentication, proper setup
94. Smart sending - Gradual volume, rotation, warm-up, conservative limits
95. Quality over quantity - Good targeting, engaging content, genuine personalization

Master these fundamentals, and you'll maintain high inbox placement even at scale.

Remember: one month of poor deliverability can take 6+ months to recover from. It's worth investing time upfront to do this right.

Want help implementing these strategies? MailSequence automates deliverability best practices so you can focus on your message, not technical configuration.

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