- Never send cold outbound from your primary domain. Dedicated sending domains are non-negotiable.
- SPF, DKIM, and DMARC must be configured on every sending domain before a single email goes out.
- Warm every domain for 3–4 weeks minimum before running sequences at volume.
- Inbox rotation across multiple mailboxes protects sender reputation at scale.
- Skip any of these and your emails go to spam — or permanently damage your domain.
WHY MOST COLD EMAIL *FAILS*
The most common Apollo.io support ticket isn't "how do I write better copy." It's "why is my reply rate 0.5%?" And in almost every case, the answer is the same: the infrastructure wasn't set up.
No dedicated sending domains. No DNS authentication. No warming. Just someone who bought a sequencing tool, loaded in a list, and hit send from their main company email.
Cold email that actually works starts with the invisible stuff — the domains, the authentication records, the warming schedule, the mailbox rotation. Get that right and the copy almost doesn't matter. Get it wrong and no amount of A/B testing will save you.
BUYING YOUR *SENDING DOMAINS*
For most early-stage companies, we start with 2–3 cold email domains and 2–3 mailboxes per domain — giving you 4–9 sending inboxes. That's enough volume to run meaningful sequences without hammering any single mailbox past safe send limits.
If your primary domain is yourcompany.com, your cold domains might be yourcompany.io, getyourcompany.com, and yourcompany.co. Same brand feel, full separation of risk.
Domain age matters for deliverability. Buy your cold domains now even if you're not ready to start — older domains warm faster and perform better from day one of sequencing.
Purchase from Google Domains, Namecheap, or Cloudflare. You'll be setting DNS records, so use a registrar you're comfortable navigating.
SPF, DKIM & *DMARC*
These three DNS records are the difference between landing in primary and going straight to spam. Email providers use them to verify that mail claiming to come from your domain actually came from your domain.
All three must be configured on every sending domain before any email goes out.
SPF
Tells receiving servers which servers are authorized to send on behalf of your domain. One TXT record per domain, takes five minutes to configure.
DKIM
Adds a cryptographic signature proving emails weren't tampered with in transit. Generated inside Google Workspace or Microsoft 365, then added to DNS. Verify with MXToolbox — propagation takes up to 48 hours.
DMARC
Tells receiving servers what to do when email fails authentication. Start with p=none (monitor mode), then move to p=quarantine and p=reject after 1–2 weeks of confirming clean authentication.
DOMAIN & INBOX *WARMING*
A new domain with new mailboxes has zero sending history. Inbox providers need to see a track record of legitimate, engaged mail before trusting you at volume. 3–4 weeks minimum. No shortcuts.
| Week | Daily Sends (per mailbox) | Sequences? |
|---|---|---|
| Week 1 | 5–10 (warm-up only) | No |
| Week 2 | 15–20 (warm-up only) | No |
| Week 3 | 25–30 + 5–10 sequences | Soft launch |
| Week 4+ | 30–50 + 20–30 sequences | Full ramp |
Sending cold volume from an unwarmed domain will tank your deliverability for months. The warm-up period is not optional.
SEQUENCES & *INBOX ROTATION*
Once mailboxes are warmed and connected to Instantly or Apollo, configure inbox rotation. This distributes sequence sends across multiple mailboxes, protecting each one's sender reputation and keeping daily sends per inbox within safe limits.
Keep daily sends per mailbox under 40–50 emails per day. If you need more volume, add mailboxes — don't push individual inboxes past that threshold.
Sequence structure: a 3-step sequence over 7–10 days outperforms a 7-step sequence in nearly every case. Step 1 is about the problem. Step 2 is the follow-up with a different angle. Step 3 is a short breakup — "still worth a conversation?" That's the playbook.
Instantly
Apollo
Clay