How to set up email deliverability for cold outreach

Cold email deliverability — getting your emails into the primary inbox instead of spam — requires four things done correctly: a separate sending domain, properly configured DNS authentication records, a warmup period before sending at volume, and daily send limits that stay under spam-trigger thresholds. Skip any of these and your reply rates will collapse within weeks as your domain gets flagged.

Why do you need a separate sending domain?

Your primary business domain (ektie.com) should never be used for cold outbound. If it gets flagged as a spam source — which happens when you send at volume to cold contacts — your company email reputation is permanently damaged. Cold outbound goes on a dedicated sending domain (ektie.io, ektie-sales.com, or similar). If that domain gets flagged, you rotate to a new one without affecting your main email infrastructure. This is not optional for any team sending more than 50 cold emails per day.

What DNS records do you need and why?

Three records are required. SPF (Sender Policy Framework): tells receiving email servers which servers are authorised to send email from your domain. DKIM (DomainKeys Identified Mail): adds a cryptographic signature to your emails that proves they weren't tampered with in transit. DMARC (Domain-based Message Authentication, Reporting and Conformance): tells receiving servers what to do with emails that fail SPF or DKIM checks — and gives you reporting on deliverability issues. All three together are the baseline for legitimate cold outbound. Missing any one of them will cause deliverability problems.

What is email warmup and how long does it take?

Email warmup is the process of gradually increasing send volume from a new domain over 3–4 weeks so receiving servers build a positive reputation for it. Start at 5–10 emails per day in week 1. Increase by 10–15 per day each week. Engage with the emails being sent — open them, reply to some, avoid them going to spam. Tools like Instantly and Mailreach automate this by running warmup exchanges between network accounts. At the end of 4 weeks, a properly warmed domain can send 40–50 cold emails per day without deliverability problems.

What daily send volume is safe?

Per mailbox: 40–50 emails per day is the safe ceiling for a well-warmed domain. Above that, spam filter algorithms start treating the volume as non-human and flag accordingly. If you need more volume, add mailboxes on additional sending domains — don't push a single mailbox beyond 50/day. For teams sending 200+ emails per day, that means 4–5 mailboxes on 2–3 separate domains, all properly configured and warmed.

How do you know if your deliverability is broken?

Three signals. Open rate below 20% on a warm, defined ICP (industry average for cold outbound is 30–45%) suggests emails aren't reaching the primary inbox. Reply rate below 1% despite good ICP targeting and tested messaging. Bounce rate above 5%. If all three are present simultaneously, check your DNS records, check if your sending domain has been blacklisted (use MXToolbox), and check your spam score before blaming the message.