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The complete checklist to ensure your cold emails land in the inbox, not the spam folder. Covers DNS authentication, domain warmup, content best practices, and ongoing monitoring.
Even the best-written cold email is worthless if it never reaches the inbox. Studies show that 20-30% of legitimate sales emails land in spam due to poor authentication, bad sending practices, or content issues. This checklist walks you through every step to maximize your inbox placement rate — from DNS setup to ongoing monitoring.
Proper DNS authentication is the foundation of email deliverability. Without SPF, DKIM, and DMARC, your emails will be flagged as suspicious by every major email provider.
SPF (Sender Policy Framework) tells receiving mail servers which IP addresses are authorized to send email on behalf of your domain. Add a TXT record to your DNS with the following value:
v=spf1 include:_spf.google.com include:sendgrid.net ~allDKIM (DomainKeys Identified Mail) adds a digital signature to every email you send, proving the email has not been tampered with in transit. Your email provider will generate a public/private key pair. Add the public key as a TXT record at your DKIM selector subdomain. Example selector record:
selector1._domainkey.yourdomain.com IN TXT "v=DKIM1; k=rsa; p=MIGfMA0GCSqGSIb3DQEBA..."DMARC (Domain-based Message Authentication, Reporting, and Conformance) ties SPF and DKIM together and tells receiving servers what to do when authentication fails. Start with a quarantine policy and monitor reports:
v=DMARC1; p=quarantine; rua=mailto:dmarc@yourdomain.com; pct=100Default tracking domains used by email platforms (e.g., sendgrid.net or mailchimp.com) are shared across thousands of senders. If another sender on the same domain gets flagged for spam, your deliverability suffers too. Set up a custom tracking domain like track.yourdomain.com to isolate your reputation and improve inbox placement.
MX (Mail Exchanger) records tell the internet where to deliver email for your domain. Ensure your MX records point to the correct mail server and have proper priority values set. Use a tool like MXToolbox to verify your records are resolving correctly and that there are no conflicts.
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New domains and mailboxes have no sending reputation. Warming up gradually tells email providers you are a legitimate sender, not a spammer. Follow this week-by-week schedule to build trust.
| Week | Daily Volume | Total/Week | Focus |
|---|---|---|---|
| Week 1 | 5-10 | 35-70 | Personal connections, warm contacts |
| Week 2 | 15-25 | 105-175 | Engaged prospects, small batches |
| Week 3 | 30-50 | 210-350 | Expand to lukewarm prospects |
| Week 4 | 50-75 | 350-525 | Start cold outreach at low volume |
| Week 5 | 75-100 | 525-700 | Increase cold volume gradually |
| Week 6+ | 100-150 | 700-1050 | Full sending volume |
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Beyond DNS authentication, these technical practices protect your sender reputation and ensure long-term deliverability as you scale your outbound campaigns.
Never send cold email from your primary domain. Use a subdomain like mail.yourdomain.com or outreach.yourdomain.com. This protects your main domain reputation if anything goes wrong with cold outreach.
TLS (Transport Layer Security) encrypts emails in transit between mail servers. Most modern ESPs support TLS by default, but verify it is enabled. Gmail and Outlook penalize emails sent without encryption.
Hard bounces (invalid email addresses) damage your sender reputation fast. Configure your ESP to automatically remove hard bounces after the first occurrence. Soft bounces should be retried 2-3 times before removal.
Choose an ESP with strong deliverability infrastructure and good IP reputation. Providers like Google Workspace, Microsoft 365, SendGrid, and Amazon SES maintain dedicated compliance teams that keep their sending IPs clean.
Include a List-Unsubscribe header in every outbound email. This is required by Gmail and Yahoo as of February 2024. It gives recipients an easy way to opt out without marking your email as spam, which protects your sender reputation.
Check your sending domain and IP against major blacklists weekly using tools like MXToolbox, MultiRBL, or Spamhaus. If you end up on a blacklist, most providers have a delisting process — act immediately to minimize damage.
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What you write matters as much as how you send it. Spam filters analyze email content, structure, and formatting to determine inbox placement. Follow these guidelines to stay out of the spam folder.
Certain words and phrases trigger spam filters. Avoid: "free", "guaranteed", "no obligation", "act now", "limited time", "click here", "buy now", "discount", "winner", "congratulations", and "100% free". Write naturally as if you are emailing a colleague.
Emails that are mostly images with little text are a strong spam signal. If you include images, make sure the email has substantially more text content. For cold outreach, plain text with no images often performs best.
Every link in your email is a potential spam signal. Cold emails with 3+ links see significantly lower inbox placement rates. Include only the most essential link — ideally just your calendar link or website.
Generic emails get flagged as spam more often because they look like bulk sends. Personalize the prospect name, company, a specific observation about their business, or a mutual connection. The more unique each email is, the better your deliverability.
Short, conversational emails perform better for cold outreach. They look like real 1-to-1 communication rather than marketing blasts. Aim for 75-150 words — enough to deliver value, short enough to respect their time.
Heavy HTML templates with styled fonts, colors, and complex layouts scream "marketing email" to spam filters. For cold outreach, use plain text or minimal HTML that mimics how a real person would write an email.
WRITING IN ALL CAPS or using multiple exclamation marks (!!!) are classic spam signals. They also make your email look unprofessional. Write in sentence case with standard punctuation.
Every cold email should have one clear ask — typically a meeting request or a question. Multiple CTAs confuse the reader and reduce reply rates. Make your CTA a question to encourage a response (e.g., "Worth a 15-minute chat this week?").
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Deliverability is not a one-time setup — it requires ongoing monitoring. These metrics and tools help you catch issues early before they impact your campaigns.
Open rates below 30% on cold email suggest deliverability issues — your emails may be landing in spam or promotions tabs. Track open rates per sending domain and per campaign to identify problems early.
A bounce rate above 3% signals to email providers that you are sending to unverified or outdated lists. Verify every email address before adding it to a campaign using tools like NeverBounce, ZeroBounce, or MillionVerifier.
If more than 0.1% of recipients mark your email as spam, your sender reputation will suffer dramatically. Gmail in particular enforces this threshold strictly. Monitor complaints through your ESP dashboard and Google Postmaster Tools.
Google Postmaster Tools is a free tool that shows your domain and IP reputation with Gmail specifically. Since Gmail represents 30-40% of business email, monitoring your reputation here is critical. Set it up at postmaster.google.com.
Before launching any campaign, send a test email to Mail-Tester.com to get a deliverability score out of 10. It checks your SPF, DKIM, DMARC, content quality, blacklist status, and more. Aim for a score of 9 or above.
Sudden spikes in sending volume trigger spam filters. Maintain a consistent daily sending pattern. If you need to increase volume, do it gradually over weeks (see the warmup schedule above). Sending at random intervals also helps mimic natural human behavior.
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Our team sets up and optimizes email infrastructure for 300+ B2B companies. We handle SPF, DKIM, DMARC, domain warmup, and ongoing monitoring so your emails always land in the inbox.