How Many Mailboxes and Domains Do You Need for Cold Email? (With Formula)
inboxy team · · 3 min read
Ask ten cold emailers how many inboxes you need and you will get ten answers. The maths is actually simple once you fix two numbers: how many emails each inbox sends a day, and how many inboxes you put on each domain.
The two safe defaults
- 30 to 50 cold emails per inbox per day, including follow-ups. We use 40 below. (Why not more? See Google Workspace sending limits.)
- 2 to 3 inboxes per domain. We use 3 below. Spreading inboxes across domains means one problem never takes down your whole operation.
The formula
Inboxes = emails per day ÷ 40
Domains = inboxes ÷ 3, rounded up
Then add about 20% spare inboxes. You will want some warming in reserve to rotate in when an inbox needs a rest, or when you scale.
Worked examples
| Emails per day | Inboxes | With 20% spare | Domains | Approx. emails per month |
|---|---|---|---|---|
| 200 | 5 | 6 | 2 | 4,400 |
| 500 | 13 | 16 | 6 | 11,000 |
| 2,000 | 50 | 60 | 20 | 44,000 |
| 10,000 | 250 | 300 | 100 | 220,000 |
Monthly figures assume 22 sending days. Remember that follow-ups count: a three-step sequence to 100 new prospects a day eventually means up to 300 sends a day.
What it costs
At inboxy's flat rate of $3 per Google Workspace mailbox a month ($2.40 on yearly billing):
- 16 inboxes: $48 a month
- 60 inboxes: $180 a month
- 300 inboxes: $900 a month
Add domains (usually $10 to $15 a year each from your registrar) and warmup if you want it at the same per-inbox rate. Try your own numbers in the pricing calculator.
Choosing domains
- Never send cold email from your main company domain.
- Use close variations: getacme.com, tryacme.com, acmehq.com.
- Prefer .com, or your country's main TLD. Cheap novelty TLDs carry more spam baggage.
- Redirect every domain to your main website so curious prospects land somewhere real.
- Set up SPF, DKIM and DMARC on every one. See our setup guide.
Common mistakes
- Too many inboxes on one domain. Ten inboxes on one domain means one complaint wave hits all ten.
- Launching on day one. New inboxes need two to four weeks of warmup. See the timeline.
- No spares. Without reserve inboxes, any rest period means your volume drops.
Skip the setup
inboxy creates Google Workspace mailboxes with SPF, DKIM and DMARC already configured, connects them to your sequencer for free and keeps them warm, at a flat $3 per mailbox a month. See pricing.
