Cold Email Deliverability Checklist: 35 Checks Before Every Campaign
Cold email deliverability is determined by domain authentication, list quality, inbox warmup, sending behavior, and message content — not any single factor alone. Use this checklist before every new campaign launch and as a monthly audit for active programs. Teams that follow structured deliverability protocols consistently achieve inbox placement above 95% and keep bounce rates below 2%.
What is cold email deliverability?
Cold email deliverability is the percentage of outbound emails that reach a recipient's primary inbox rather than the spam or promotions folder. It is determined by domain reputation, list quality, authentication setup, and message content — not just sending volume.
Domain and sending infrastructure
These are the non-negotiables. Without proper authentication, inbox providers cannot verify your emails are legitimate — and will treat them as suspicious by default.
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- SPF record configured — DNS TXT record listing authorized sending servers for your domain. Verify with MXToolbox.
- DKIM signature active — cryptographic signature added to outgoing mail. Confirms messages haven't been altered in transit. Configure via your sending platform or DNS provider.
- DMARC policy set — tells inbox providers how to handle mail failing SPF/DKIM checks. Minimum:
p=noneto start collecting data; move top=quarantineorp=rejectonce monitoring confirms clean setup. - Dedicated sending domain in use — never cold-send from your primary company domain. Use a subdomain (mail.yourcompany.com) or a mirror domain (trycompany.com). Domain reputation damage on a cold-sending domain should not affect your core email.
- Domain is not on any blacklists — check MXToolbox Blacklist, Spamhaus, and Barracuda before every campaign. A single blacklisting can drop inbox placement from 95%+ to under 50% overnight.
- Sending IP is not shared with high-risk senders — if using a shared IP (common with email service providers), verify the IP's reputation history.
Inbox warmup
New domains have no sending history and no reputation. Inbox providers treat them as unknown — and unknown senders default to spam or promotions. Warmup builds the reputation layer before campaign volume starts.
- Warmup started at least 14 days before first campaign — 30 days is safer for cold outreach at scale
- Starting volume set at 20–30 emails/day — do not start higher regardless of how urgent the campaign timeline is
- Volume increasing 10–15% every 3–5 days — gradual ramp tied to actual reply signals, not a fixed calendar schedule
- Warmup emails include real replies — automated warmup tools that only send to each other without real human reply signals provide weaker reputation building. Mix in genuine outreach to warm the domain authentically.
- No campaign volume launched before warmup period ends — the most common mistake. Sending 500 emails/day from a 3-day-old domain is the fastest way to get it flagged.
List quality
List quality is the single largest controllable variable in deliverability. Unverified lists generate hard bounces, catch-all failures, and spam complaints that erode domain reputation faster than any sending volume mistake.
- List verified for email accuracy — use a real-time validation tool. Target under 2% estimated bounce rate before sending. SalesOutreach validates contacts at 95%+ accuracy before they enter sequences.
- Hard bounces from prior campaigns suppressed — any address that hard-bounced previously must be removed and never re-sent to.
- Role-based addresses removed — info@, support@, sales@, contact@ addresses are catch-alls or shared inboxes that generate spam complaints, not replies. Remove them.
- Unsubscribes honored and suppressed — anyone who has opted out of prior communications must be suppressed across all sequences.
- Catch-all domains flagged or removed — catch-all domains accept all email regardless of whether the address exists, making them useless for deliverability signaling. Remove or deprioritize unless your platform can validate at the subdomain level.
- List sourced from verified provider — industry average email accuracy from most data providers is 70–85%. Verify the accuracy SLA of your data source before building campaigns on it.
Sending behavior
How you send matters as much as what you send. Inbox providers pattern-match sending behavior — unusual volume spikes, sending outside business hours at scale, or blasting the same content to thousands of addresses simultaneously all trigger spam filters.
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- Daily send volume within warming limits — no more than 20–30% increase from previous week's volume without a corresponding improvement in positive reply signals
- Send schedule limited to business hours in recipient time zone — sending at 2am does not affect deliverability directly, but it affects reply rate, which affects reputation signals
- Send intervals randomized — do not send all emails in a campaign at identical intervals (e.g., one email every 60 seconds). Randomize within a window to simulate human behavior.
- Bounce rate monitored per campaign, not just per month — a bounce spike in campaign 3 that is caught at campaign 4 has already damaged reputation. Check after every campaign.
- Reply rate tracked and used as pacing signal — if positive reply rate drops below 1%, pause and investigate before scaling volume.
- Complaint rate below 0.1% — Google and Yahoo's 2024 bulk sender requirements set complaint rate thresholds that will result in deliverability downgrades if exceeded.
Email content
Spam filters are increasingly sophisticated. Modern spam classification looks at content patterns, link structure, and content-to-image ratio — not just keyword matching.
- Plain text format used — HTML formatting with images, buttons, and tracked links signals marketing automation, not personal outreach. Use plain text or minimal formatting.
- No spam trigger words — avoid: "guarantee", "free", "click here", "urgent", "limited time", "100%". Use SalesOutreach's spam words checker before sending.
- Under 3 links per email — multiple links increase spam score. For cold email, zero or one link is ideal.
- No image attachments in first touch — attachments trigger attachment-based spam scanning and significantly increase spam placement risk.
- Unsubscribe option included — required for CAN-SPAM compliance and good deliverability hygiene. A clearly stated "reply with 'remove' to opt out" in the footer is sufficient.
- Email personalized beyond first name — generic "Hi [First Name]" personalization provides no spam filtering benefit. Specific, relevant content reduces spam classification risk.
Ongoing monitoring
Deliverability is not a one-time setup. It requires regular monitoring to catch reputation drift before it becomes a crisis.
- Google Postmaster Tools connected — monitors domain reputation, spam rate, and authentication status for Gmail recipients (typically 50–60% of B2B contacts)
- Blacklist monitoring active — weekly check of MXToolbox Blacklist and Spamhaus for all sending domains
- Bounce rate reviewed weekly — target under 2% per campaign; investigate immediately if it exceeds 3%
- Spam complaint rate reviewed weekly — target under 0.1% per send; Google enforcement begins above 0.3%
- Reply rate by segment tracked — a drop in reply rate from a specific ICP segment is an early signal of deliverability degradation in that segment before global reputation impact appears
Before every new campaign launch
Run these checks within 48 hours of launching any new campaign:
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- Sending domain not on any current blacklists (MXToolbox check)
- List re-verified if more than 30 days old — data decays at approximately 2% per month
- All suppression lists applied — hard bounces, unsubscribes, already-contacted leads
- First 50 sends manually reviewed for inbox placement — use a seed list tool or manual test accounts at Gmail, Outlook, and Yahoo before scaling volume
- Positive reply rate from prior campaigns above 1% — do not launch a new campaign if the previous campaign's positive reply rate was below this threshold without first identifying and fixing the cause
Deliverability benchmarks: what "good" looks like in 2025
Use these as reference points when evaluating your campaign performance:
| Metric | Target | Investigate if |
|---|---|---|
| Inbox delivery rate | 95%+ | Below 90% |
| Bounce rate (hard) | < 2% per campaign | Above 3% |
| Spam complaint rate | < 0.1% | Above 0.3% |
| Positive reply rate | 3–8% (well-targeted) | Below 1% |
| Unsubscribe rate | < 0.5% | Above 1% |
Industry averages as of 2025: B2B average cold email delivery rate ~98%, average open rate ~27–28% (treat as directional due to privacy tracking changes), average bounce rate ~2%.
How SalesOutreach automates these checks
Many of the checks in this list are handled automatically by SalesOutreach before and during campaigns:
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- List quality: Real-time email validation at 95%+ accuracy before contacts enter sequences
- Sender health monitoring: Continuous tracking of bounce rate, positive reply signals, and spam trends — with automatic pacing adjustments
- Suppression management: Hard bounces, unsubscribes, and already-contacted leads are automatically suppressed across campaigns
- Spam content guidance: Built-in spam words checker and cold email grader flag high-risk content before sending
- Domain authentication guidance: Onboarding flow includes step-by-step SPF, DKIM, and DMARC setup for new sending domains
For teams running outbound without a dedicated RevOps function, having these controls automated in the platform significantly reduces the operational overhead of maintaining deliverability at scale.
FAQ
What is the most common reason cold emails go to spam?
The most common cause is sending to unverified lists with high bounce rates. A bounce rate above 2% signals to inbox providers that the sender is using low-quality data, triggering spam filter escalation. Secondary causes include missing SPF/DKIM/DMARC authentication and message content that matches known spam patterns.
How do I set up SPF, DKIM, and DMARC for cold email?
SPF is a DNS TXT record that authorizes which servers can send mail from your domain. DKIM adds a cryptographic signature to outgoing mail. DMARC tells inbox providers what to do with mail that fails SPF/DKIM checks (monitor, quarantine, or reject). All three must be configured in your domain's DNS settings — verify with MXToolbox or Google Postmaster Tools after setup.
How long does inbox warmup take for a new sending domain?
Inbox warmup for a new domain takes 14–30 days minimum. Start at 20–30 emails per day and increase by 10–15% every 3–5 days as positive reply signals build. Using a warmup tool accelerates the process but does not replace gradual manual ramp — automated warmup alone without real replies can still trigger filtering at volume.
Can I send cold email from my main company domain?
Avoid sending cold outreach from your primary company domain. If cold sending damages sender reputation, it affects all email from that domain — including transactional and marketing messages. Use a dedicated sending domain (e.g., mail.yourcompany.com or trycompany.com) for all cold outreach.
What bounce rate is acceptable for cold email?
Keep hard bounce rate below 2% per campaign. Above 2%, inbox providers begin to flag the sending domain as a risk. If bounce rate hits 3%+, pause, re-verify your list, and suppress all hard bounces before resuming. SalesOutreach validates contacts at 95%+ accuracy before sending to reduce bounce exposure.
How often should I check my domain sender reputation?
Check sender reputation monthly at minimum — weekly during active high-volume campaigns. Use Google Postmaster Tools for Gmail delivery insights, MXToolbox for blacklist checks, and your ESP's bounce and spam complaint dashboards. A sudden reputation drop requires immediate investigation before resuming sends.
What is DMARC and why does it matter for cold email?
DMARC (Domain-based Message Authentication, Reporting, and Conformance) is a DNS policy that tells inbox providers how to handle mail that fails SPF or DKIM checks. Without DMARC, providers may accept spoofed emails appearing to come from your domain. With DMARC set to "quarantine" or "reject," your domain is protected and sender reputation signals are cleaner.
How does list quality affect cold email deliverability?
List quality is the single largest controllable variable in deliverability. Unverified lists carry stale, invalid, and role-based addresses that generate hard bounces and spam complaints. A list with 5% invalid emails will damage sender reputation within the first campaign. Verifying lists before sending — targeting under 2% estimated bounce rate — is the highest-leverage deliverability action before any campaign launch.
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