What is cold email domain warming?
Warming is the process of establishing a sending reputation for a brand-new domain and mailbox by starting at very low volume and increasing gradually, while generating positive engagement signals: opens, replies, messages moved out of spam. For a complete guide, see our inbox warmup guide.
Inboxlogy Infrastructure Stats
- 0 account suspensions in company history (October 2026)
- 0 customers locked out of their mailboxes — ever
- $2.80/mailbox/month at 500+ scale
- 100% ownership — full admin access
In practice, "warmup" today means an automated peer network inside your sending tool. Instantly, Smartlead, and ReachInbox each run a pool: your mailbox sends small numbers of messages to other users' mailboxes in the pool, those mailboxes reply, mark as important, and rescue anything that lands in spam. Compare these tools in our Google Workspace vs M365 comparison.
❌ Without Proper Warmup
- Domain flagged as spam within days
- 0% inbox placement
- Wasted domain + time
✅ With Inboxlogy + Warmup
- Gradual reputation building
- 85-95% inbox placement
- Ready in 3-4 weeks
How long should you warm a new domain?
Plan on 3–4 weeks from domain registration to first cold send.
- Days 1–3: Register and configure, send nothing. Publish SPF/DKIM/DMARC/MX.
- Days 4–7: Create mailboxes, connect them, start warmup at minimum volume.
- Weeks 2–3: Ramp warmup.
- Week 3 or 4: Begin live sending at low volume.
Safe warmup ramp schedule
- Week 1: 2–5 messages/day. No live campaigns.
- Week 2: 10–20/day. Still no live campaigns.
- Week 3: Begin live sending at 5–10/day while warmup continues.
- Week 4: Live sending 15–20/day.
- Week 5+: Steady state at 20–35/day per mailbox.
How many mailboxes and domains do you need?
Work backwards from your target volume:
- Mailboxes needed = (monthly volume ÷ 21 working days) ÷ 30 sends/day
- Domains needed = mailboxes ÷ 3
📊 Capacity Calculator
| Prospects/mo | Mailboxes | Domains | Cost* |
|---|---|---|---|
| 2,500 | 10 | 4 | $50/mo |
| 5,000 | 20 | 7 | $100/mo |
| 10,000 | 40 | 14 | $200/mo |
| 25,000 | 100 | 34 | $280/mo |
*Inboxlogy pricing: $4.99 (1-99) or $2.80/mailbox (500+)
What is inbox rotation?
Inbox rotation means a single campaign distributes its sends across many mailboxes instead of one. Learn more in our rotation playbook. The rules:
- Set a per-mailbox daily cap in the tool
- Keep the whole thread on one mailbox
- Vary the copy across mailboxes (3–5 variants)
- Add randomized delays (60–180 seconds)
- Restrict to business hours, weekdays only
DNS records every cold email domain needs
✅ Inboxlogy configures all DNS automatically
Which sending limits matter?
Policy limits: Google allows 2,000/day. Microsoft allows 10,000/day. See our daily sending limits guide.
Reputation limits: 30–50 sends/day per mailbox. You will destroy deliverability at 2% of your policy limit.
"Bulk senders must keep spam rates below 0.3%."
— Google Email Sender Guidelines, February 2024
How to monitor deliverability
- Reply rate per domain — your best placement proxy
- Bounce rate per domain
- DMARC aggregate reports — what is DMARC?
- Blocklist checks (blacklist checker guide)
- Manual inbox checks
When deliverability drops
- Pause the affected domain's campaigns
- Read the bounce messages
- Re-verify the segment
- Check authentication (DNS) — use our free DNS checker
- Cut volume by 60–70% for 7–10 days
FAQ
How many cold emails per day can one mailbox send?
20–35/day after 2–4 week warmup. See our full deliverability guide.
Should I keep warmup running after campaigns go live?
Yes, at 5–15/day per mailbox.
Can I use subdomains instead of buying separate domains?
Possible but weaker protection. Subdomains inherit parent reputation. Learn more about buying domains for cold email.