TL;DR
New domains should warm up for 2–4 weeks before sending real campaigns, starting at 10–20 emails/day and capping out at 30–50/day per domain for sustained campaigns. With multiple warmed domains running in rotation, total volume can reach 500–2,000+/day without domain damage.
The answer is almost always "fewer than you think, from more domains than you have."
Why domain volume matters: Every email domain has a reputation score. Send too many emails too fast and Gmail and Outlook flag you as a spammer — your emails go to junk and open rates crater. Recovering a burned domain is very hard.
Domain warm-up protocol: - Week 1: 10–20 emails/day from the new domain - Week 2: 20–30/day - Week 3: 30–40/day - Week 4+: Steady state at 30–50/day
Do this in parallel across 5–10 domains and you can send 200–500 emails/day sustainably within 30 days.
The multi-domain infrastructure approach (what high-volume teams do):
Buy 10+ domains (variations of your main domain: get-acme.com, trykacme.com, heyacme.com). Warm all of them simultaneously using Instantly or Smartlead's warm-up network (400K+ accounts). Once warmed, rotate sends across all domains. This is how you send 1,000–2,000 emails/day without ever burning a domain.
What "per day per domain" limits look like: - Newly warmed domain: Max 30–50 sends/day - Well-warmed domain (3+ months old, good reputation): 50–80 sends/day - Your primary company domain: Never use for cold outreach — protect it for transactional email
Quality vs. quantity tradeoff: More emails with worse personalization will produce lower reply rates and higher risk than fewer, better emails. Most startups are better off sending 100 highly personalized emails at 8% reply rate (8 meetings) than 500 generic emails at 1% (5 meetings) — and destroying their domain in the process.
Tooling: Instantly.ai is built specifically for this — unlimited domains on paid plans, best-in-class warm-up, and built-in rotation across domains.
From Cactus: Cactus manages cold email infrastructure for clients running 500–2,000 sends/day — our standard setup is 10–20 warmed sending domains rotated through Instantly with a clean separation from the client's primary domain.
Cactus Marketing embeds with B2B tech startups to turn strategy into pipeline. We've worked with 60+ companies, supported 12 exits, and contributed to $7B+ in client valuations.
Book a free 30-minute call — we'll give you a concrete plan for your situation.
Book a free strategy call →How do I write a cold email that gets replies?
Write one sentence that's specifically about them, one sentence on their problem, one on your solution, and one CTA. The email should be under 80 words, reference something real about their company, and ask a yes-or-no question at the end.
How do I find leads for cold email?
Start with Apollo.io or LinkedIn Sales Navigator to build a list from your ICP criteria. Enrich it through Clay or a waterfall of data providers for verified emails. Target trigger events — recent funding, new hires, job postings — to catch companies in active buying moments.
What is a good cold email reply rate?
A good cold email reply rate is 3–8% for a broad ICP campaign and 8–15% for a highly personalized, trigger-event-based campaign. Anything above 15% with meaningful volume is excellent. Below 2% means something fundamental is wrong — ICP, targeting, or the email itself.
How do I warm up an email domain?
Buy a new domain, set up Google Workspace or Microsoft 365, configure SPF/DKIM/DMARC, then use a warm-up tool (Instantly, Smartlead) to automatically exchange emails with a network of inboxes over 3–4 weeks before sending real cold email.