Secondary domain
dfyautomationhq.com
- Sends cold email only
- Holds a few inboxes
- Redirects to the main site
Common patterns: yourbrandhq.com tryyourbrand.com getyourbrand.com
Cold email inbox calculator.
Pick how many cold emails you want to send a day. See the inboxes and domains you need on Google, on Azure or half and half, what each setup costs, and every step of the math.
Divide your daily volume by what one inbox sends (15 a day on Google, 4 on Azure), then by the inboxes on each domain (3 on Google, up to 75 on Azure). At 2,000 emails a day, that's 134 Google inboxes on 45 domains, or 500 Azure inboxes on 7.
The providers we use for our clients
Some of these are affiliate links: we may earn a commission at no cost to you. We only list tools we use for client campaigns.
02 / Domains
Your main domain never sends cold email.
Before you count inboxes: cold email goes out from secondary domains that look like yours, so your main domain stays safe. Anyone who clicks one lands on your real website.
Main domain
dfyautomation.io
- Clients, invoices, proposals
- Your team's everyday email
- Never sends cold email
Your main domain stays safe. If a secondary domain gets flagged, your client emails still land. Google's spam complaint limit is 0.3%, and it recommends staying under 0.1%.
03 / Spamhaus
Check your domains on Spamhaus.
Every domain you send from needs watching. Spamhaus keeps a free blocklist of domains flagged for spam, and a burnt domain shows up there.
- Check your main domainBefore anything else.
- Check every secondary domainEvery week.
- Listed means burntStop sending from it and replace it.
04 / Calculator
What it costs at your volume.
Now size it. Pick how many cold emails you want to send a day to see the inboxes and secondary domains you need, and what they cost. Every result shows its math.
Change the numbers
Example prices, November 2026. Monthly prices are the inbox subscriptions. Domains are paid once a year, so they're added to the first month. Why these numbers? Read Google vs Azure inboxes for cold email.
How many inboxes per domain should I use for cold email?
On Google Workspace, 3 inboxes per domain at 15 emails a day each, so 45 emails a day per domain. On Azure, up to 75 inboxes per domain at 4 emails a day each, so 300 emails a day per domain.
How many emails should one inbox send a day?
In the setups we run, a Google inbox sends 15 cold emails a day and an Azure inbox sends 4. Divide your daily volume by that number and round up to get the inboxes you need.
Google or Azure inboxes for cold email?
Azure is cheaper at volume: from 2,000 to 5,000 emails a day, an all-Azure setup costs about 44% less than all Google over the first year, domains included. The trade-off is that much more volume sits on each Azure domain, so spam complaints add up faster per domain.
How do I check if my domain is on Spamhaus?
Search the domain on check.spamhaus.org. It's free. Check your main domain first, then every secondary domain regularly. If a domain is listed, it's burnt: stop sending from it and replace it.
06 / Book a call
Let's talk about your go-to-market.
An obligation-free 30-minute strategy call with Ali and Javeria, whether you want us to run it, build it, or you're not sure yet.
- 01Tell us what you're looking for, then pick a time.
- 02On the call, we look at your goals, your team and how you sell today.
- 03You get an honest recommendation. If we're a fit, a written plan and proposal follow.
Rather talk now?