Your cold email can have the perfect hook and the strongest CTA on earth — and still fail. If the inbox never sees it, none of that matters. Deliverability is the silent killer of cold outreach: industry studies regularly find 15-25% of cold emails land in spam, and for new sending domains that number can hit 50%+.
Here's the checklist I run before every send. Miss any of these and your reply rate is dead on arrival.
1. SPF record (proves who can send for your domain)
An SPF TXT record lists the servers allowed to send email as your domain. If your cold email tool sends through its own infrastructure, its IPs must be in your SPF. Without it, receiving servers treat your mail as unverified.
2. DKIM signing (proves the message wasn't tampered)
DKIM attaches a cryptographic signature to each email. Most modern cold email tools sign for you, but you must publish their DKIM records in your DNS. Check that your tool's "DKIM status" shows passing, not pending.
3. DMARC policy (tells inboxes what to do with failures)
DMARC ties SPF and DKIM together and tells receiving servers what to do when both fail. Start with p=none to monitor, then move to p=quarantine once you're clean. No DMARC = reputation signals ignored.
4. Custom tracking domain (stop sharing reputation)
Free tiers of most tools send links through a shared domain. If another customer spams through that domain, your emails inherit the damage. A custom tracking domain keeps your link reputation yours.
5. Warm-up before volume (build sending reputation slowly)
New domains have zero reputation. Ramp from ~5-10 emails/day to your target volume over 2-4 weeks, interacting with the warm-up inboxes. Jumping straight to 200/day from a fresh domain is the fastest way to get blacklisted.
6. Bounce rate under 2% (verify addresses first)
A bounce rate above 2-5% tells inboxes your list is stale — and that's a spam signal. Verify every address before sending. One hard bounce per thousand is acceptable; five per hundred is a reputation emergency.
7. Plain text first (spam filters distrust heavy HTML)
Pure HTML emails with no plain-text alternative look like marketing automation. Keep images minimal — some filters score them as spam bait.
8. One clear CTA (matching filters flag link-dumping)
A wall of links is a classic spam pattern. One primary CTA per email, ideally one or two links total, pointing to your site or a booking page. Multiple trackers, image links, and shortened URLs all raise suspicion.
9. Consistency of sender identity (name, domain, reply-to aligned)
If your From name and From domain and reply-to all point at different places, that's a mismatch inboxes score negatively. Keep sender name, domain, and reply-to consistent and recognizable.
10. Engagement monitoring (spam complaints under 0.1%)
Complaints (people hitting "Report spam") above ~0.1% get you throttled or blocked. Track replies, opens, and complaints weekly. No replies at all after 200 sends usually means a deliverability problem, not a copy problem.
The score that matters
The fastest check: paste your draft into a tool that scores deliverability before you send. A 95+ score doesn't guarantee a reply — but a 70 score almost guarantees you'll never know what your copy could have done, because nobody saw it.
Bottom line
- Verify your DNS records (SPF/DKIM/DMARC) before your first send
- Warm up a new domain over 2-4 weeks
- Keep bounce rate under 2%, complaints under 0.1%
- Text-first, one CTA, consistent identity
- Check every draft's deliverability score before hitting send
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