What is SPF, DKIM, and DMARC for cold email?

SPF (Sender Policy Framework) is a DNS record that authorizes specific servers to send email on behalf of your domain. DKIM (DomainKeys Identified Mail) adds a cryptographic signature to outgoing emails so receiving servers can verify they have not been tampered with. DMARC (Domain-based Message Authentication, Reporting, and Conformance) tells receiving mail servers what to do when emails fail SPF or DKIM checks — quarantine or reject them. All three must be configured for reliable cold email deliverability in 2026.

How long does it take to warm up a cold email domain?

A new sending domain typically takes 3–6 weeks to warm up to the volume needed for a cold email campaign. Start at 10–20 emails per day in week 1, increase by 20–30% each week, and monitor open rates and bounce rates throughout. Jumping to high volume before the warmup is complete causes spam placement that can take weeks to recover from.

Do cold email spam trigger words actually matter?

Yes, but they are a secondary factor compared to DNS authentication and sender reputation. Common spam trigger words in cold email include: "free," "guarantee," "limited time," "act now," "risk-free," "no obligation," and "click here." Spam filters have become more sophisticated and now evaluate the overall content pattern and sender reputation rather than just keyword matching, so domain and sending behavior matter more than individual words.

Cold Emails Going to Spam: Complete Fix Guide (2026)

Q: Why are my cold emails going to spam?

Cold emails go to spam for five main reasons: missing or misconfigured DNS authentication (SPF, DKIM, DMARC), sending too fast on a new or cold domain, spam trigger words in the copy, a poor sender reputation from previous bounces or complaints, and sending to unverified or low-quality lists with high bounce rates. DNS authentication is the highest-leverage fix — without SPF/DKIM/DMARC, Gmail and Outlook will route your email to spam regardless of copy quality.

Q: How do I fix cold emails going to spam?

Fix cold email spam placement in this order: (1) Verify SPF, DKIM, and DMARC DNS records are set up correctly for your sending domain; (2) Check your sender reputation using MXToolbox or Google Postmaster Tools; (3) Ramp your sending volume slowly — start at 10–20 emails per day on a new domain and increase by 20–30% per week; (4) Clean your list — remove bounced, unsubscribed, and unverified addresses; (5) Remove spam trigger words from your copy; (6) Test inbox placement with a tool like mail-tester.com before running campaigns.

Q: How do I check my cold email deliverability?

Test cold email deliverability by: (1) sending a test email to mail-tester.com and checking your score (aim for 9+/10); (2) checking DNS records at MXToolbox.com; (3) monitoring sender reputation at Google Postmaster Tools (postmaster.google.com); (4) checking domain blacklists at MXToolbox Blacklist Check; (5) monitoring your open rates over time — a sudden drop from 30%+ to under 15% usually indicates a deliverability problem.

Short answer: Cold emails go to spam because of missing DNS authentication (SPF/DKIM/DMARC), sending too fast on a new domain, a damaged sender reputation, or spam trigger words in the copy. DNS authentication is the highest-leverage fix — without it, Gmail and Outlook route your email to spam regardless of how good the copy is. This guide covers every cause and exactly what to do.

Spam placement is one of the most fixable cold email problems — but only if you diagnose the right cause. The fixes for a DNS authentication problem are completely different from the fixes for a sender reputation problem. Work through this in order.

Step 1: Confirm it is actually a deliverability problem

Before fixing deliverability, confirm that deliverability is actually the issue. A common mistake is diagnosing spam placement when the real problem is low open rates caused by poor subject lines or a cold, unengaged list.

The deliverability signal is your open rate:

Open rate under 15% — likely a deliverability problem (spam placement, or DNS auth failure)
Open rate 15–30% — marginal. Could be deliverability or poor targeting/subject lines. Test both.
Open rate 30%+, reply rate under 2% — deliverability is fine. The problem is your offer or copy. See our guide on why cold emails don't get replies.

If you have confirmed low open rates, start the fix sequence below.

Step 2: Check your DNS authentication (highest priority)

DNS authentication for cold email requires three records: SPF (Sender Policy Framework) authorizes your sending servers, DKIM (DomainKeys Identified Mail) cryptographically signs your emails, and DMARC tells receiving servers what to do when authentication fails. Without all three, Gmail and Outlook treat your email as suspicious and route it to spam — regardless of your content.

In February 2024, Google and Yahoo began enforcing stricter requirements for bulk senders: SPF or DKIM authentication is now required, and DMARC is strongly recommended. Any domain sending cold email without these configured will see severe deliverability degradation.

How to check your DNS auth

Go to MXToolbox.com and run these checks for your sending domain:

Check	Tool	What to look for
SPF	MXToolbox SPF Lookup	Should show a valid SPF record with your sending IP or provider authorized
DKIM	MXToolbox DKIM Lookup (need to know your DKIM selector)	Should return a valid public key
DMARC	MXToolbox DMARC Lookup	Should show a DMARC policy — at minimum `p=none` to start, `p=quarantine` for better protection

If any of these are missing or misconfigured, fix them in your domain registrar's DNS settings. Your cold email platform (SilverMailer, Smartlead, Instantly) will provide the exact DNS records to add. After adding records, propagation takes up to 48 hours.

How to add SPF for a new sending domain

Add a TXT record to your domain DNS:

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

Replace include:_spf.yourprovider.com with the SPF include provided by your email sending provider. The ~all (soft fail) is safer to start than -all (hard fail) while you are validating your configuration.

How to set a DMARC policy

Add a TXT record on _dmarc.yourdomain.com:

v=DMARC1; p=none; rua=mailto:dmarc@yourdomain.com

Start with p=none (monitoring only) before moving to p=quarantine. The rua address receives aggregate reports about your authentication failures — use these to debug before enforcing policy.

Step 3: Check your sender reputation

Even with perfect DNS auth, a damaged sender reputation will get your emails filtered. Sender reputation is tracked at the domain level and the IP level by major inbox providers.

Check your domain reputation using:

Google Postmaster Tools (postmaster.google.com) — free, shows your domain reputation with Gmail specifically. The most important signal for B2B cold email.
MXToolbox Blacklist Check — checks your sending domain and IP against major blacklists
Sender Score (senderscore.org) — IP-level reputation score from 0–100; anything under 70 is problematic

If you are blacklisted, the fix depends on which blacklist. Most blacklists have a delisting request process — submit a request, fix the underlying issue (usually high bounce rate or spam complaints), and wait. Some blacklists delist automatically after 30 days of clean sending.

Step 4: Check your sending volume and ramp schedule

Domain warmup is the process of gradually increasing sending volume on a new or cold domain so inbox providers build positive sending history before high-volume sends begin. Skipping warmup — or ramping too fast — is one of the most common causes of spam placement for founders running their first cold email campaigns.

When you start sending from a new domain, Gmail and Outlook have no history with it. Sending 500 emails on day one from a domain with zero track record triggers spam filters almost universally.

Recommended ramp schedule for a new sending domain:

Week	Daily send limit	Notes
Week 1	10–20 emails/day	Warm sends only — use a warmup service or send to known contacts first
Week 2	20–40 emails/day	Monitor open rates; should be 30%+
Week 3	40–80 emails/day	Start cold campaign sends if open rates are healthy
Week 4	80–150 emails/day	Full campaign mode for most solo operator volumes
Month 2+	150–300 emails/day	Increase only if sender reputation is healthy

Compass sets an automated ramp schedule as part of every campaign it builds — it will not let you launch at full volume before the domain is ready.

Step 5: Clean your list

High bounce rates are one of the fastest ways to damage sender reputation. When more than 2–3% of your sends result in hard bounces (invalid email addresses), inbox providers begin treating your domain as a spam source.

Before every campaign:

Verify email addresses with a tool like ZeroBounce, NeverBounce, or Hunter Email Verifier
Remove any email that comes back as “invalid,” “catch-all,” or “risky”
Never buy or scrape lists without verification — these have extremely high bounce rates
Remove unsubscribes immediately and keep them out of future campaigns

A smaller, verified list will almost always outperform a larger unverified one — both in deliverability and in reply rate.

Step 6: Audit your copy for spam triggers

Modern spam filters evaluate the full content pattern of your email, not just individual words. That said, certain phrases still reliably trigger spam classification and should be removed from cold email copy.

Common cold email spam trigger phrases:

Avoid	Use instead
“This is not spam”	(just don't say it)
“Free” (in subject lines especially)	“Complimentary” or restructure the offer
“Guarantee” / “Guaranteed”	“We commit to” / “Your [outcome] or we'll [fix]”
“Limited time offer”	State a specific date or condition
“Act now” / “Don't miss out”	Give a concrete reason for urgency
“Click here”	Descriptive link text
“Earn money” / “Make money”	State the outcome specifically
“No obligation”	“No prep needed” or similar

Also avoid: excessive exclamation points, ALL CAPS in subject lines, large images (image-only emails get heavily filtered), and more than one link in the email body. Plain-text or HTML-light emails consistently outperform image-heavy ones for deliverability.

Step 7: Test inbox placement before sending

Before launching any cold email campaign, send a test email through your sequence to mail-tester.com. It will score your email from 1–10, flag specific issues (spam words, missing auth, formatting problems), and show you whether you are likely to land in the inbox.

Target score: 9+/10. Anything under 8 has specific fixable issues — the tool will tell you what they are.

SilverMailer's Inbox Placement feature automates this: it sends your copy test to mail-tester.com, fetches the score, and surfaces the specific issues alongside your DNS auth status — all before you launch.

The full deliverability checklist

Before every cold email campaign, verify:

☐ SPF record set and valid (MXToolbox SPF Lookup)
☐ DKIM configured with your sending provider
☐ DMARC record present (minimum p=none)
☐ Domain reputation healthy in Google Postmaster Tools
☐ Not on any major blacklists (MXToolbox Blacklist Check)
☐ List verified — bounce rate expected under 2%
☐ Sending volume appropriate for domain age and warmup stage
☐ Copy tested at mail-tester.com (score 9+/10)
☐ Unsubscribe link present in all emails
☐ No spam trigger phrases in subject line or body

What to do when deliverability is already damaged

If your domain reputation is already poor — open rates under 10%, blacklist hits, low Sender Score — the recovery process takes time. There is no instant fix for a damaged domain reputation.

Recovery steps, in order:

Stop all sending immediately from the damaged domain. Continuing to send makes it worse.
Fix the root cause — DNS auth, bounce rate, spam complaints — before resuming.
Request delisting from any blacklists via their respective request forms.
Set up a new sending subdomain (e.g., outreach.yourdomain.com) to isolate cold email sending from your main domain.
Warm the new subdomain from scratch following the ramp schedule above.
Monitor Google Postmaster Tools weekly until reputation shows as “High.”

Recovery typically takes 4–8 weeks of clean sending before open rates return to normal. Running a warmup service during this period (automated warmup sends between real mailboxes) accelerates reputation repair.

Frequently asked questions

Why are my cold emails going to spam?

Most commonly: missing or misconfigured SPF/DKIM/DMARC, sending too fast on a new domain, a damaged sender reputation from previous bounces or complaints, or spam trigger words in the copy. Check DNS authentication first — it is the highest-leverage fix.

How do I fix cold emails going to spam?

In order: verify SPF/DKIM/DMARC at MXToolbox, check sender reputation in Google Postmaster Tools, confirm your ramp schedule is appropriate for domain age, clean your list to remove invalid addresses, remove spam trigger words from copy, and test with mail-tester.com before sending.

What is SPF/DKIM/DMARC?

SPF authorizes which servers can send email from your domain. DKIM adds a cryptographic signature that receiving servers use to verify your email's authenticity. DMARC tells receiving servers what to do when authentication fails. All three are required for reliable cold email deliverability in 2026.

How long does domain warmup take?

3–6 weeks to reach campaign volume safely. Start at 10–20 emails per day and increase by 20–30% per week. Skipping warmup causes spam placement that takes weeks to recover from.

Do spam trigger words actually matter?

Yes, but they are a secondary factor compared to DNS auth and sender reputation. Spam filters evaluate overall content patterns and sender history more heavily than individual words. Fix authentication and reputation first, then audit copy for trigger phrases.

How do I check my cold email deliverability?

Send a test email to mail-tester.com (aim for 9+/10), check DNS records at MXToolbox, monitor domain reputation at Google Postmaster Tools, and check blacklists at MXToolbox Blacklist Check. Monitor open rates over time — a sudden drop usually indicates a deliverability event.