Set up sending domains that protect your main one

What it does

Cold email from your main domain is a bet with your whole company’s inbox. If too many people mark it as spam, your invoices, onboarding emails and replies to customers start landing in spam too. Send cold email from separate domains that look like yours, set up properly, warmed up and sized to what you actually send.

What you need

• A domain registrar, or a sending tool that buys and sets up domains for you (Instantly and others do)
• Google Workspace or Microsoft 365 inboxes, or your sending tool’s own
• How many new people you plan to reach a week

How it works

1. 1

   Keep cold email off your main domain

   Your main domain is for customers, invoices, your team and your replies. Nothing cold goes out from it, ever.

2. 2

   Buy lookalike domains

   Variations a buyer would recognize: get[yourname].com, try[yourname].com, [yourname]hq.com. Point each one at your website, so anyone who checks lands somewhere real.

3. 3

   Set up SPF, DKIM and DMARC

   These three records prove your mail is really yours. Most sending tools set them up for you or walk you through it. Check each domain with a free checker before anything sends from it.

   A starting DMARC record, at your domain’s DNS

   Type: TXT
   Host: _dmarc
   Value: v=DMARC1; p=none; rua=mailto:dmarc-reports@[YOURDOMAIN].com

4. 4

   Three inboxes per domain, 30 cold emails a day per inbox

   Low volume per inbox and per domain keeps each one looking like a person writing, not a machine.

5. 5

   Warm every inbox up for 14 days

   Turn on warmup in your sending tool and leave it on, even after you start. No cold email goes out from a new inbox before day 14.

6. 6

   Size it to your volume

   Google Sheets: paste into A1

   New people you'll reach a week	300
   Emails each person gets	3
   Sends a working day	=ROUNDUP(B1*B2/5,0)
   Inboxes, at 30 a day each	=ROUNDUP(B3/30,0)
   Domains, at 3 inboxes each	=ROUNDUP(B4/3,0)

7. 7

   Watch it every day

   Bounces and spam complaints, per inbox. Google’s sender guidelines ask senders to keep their spam rate below 0.1% and never reach 0.3%. If one inbox slips, pause that inbox, not the whole campaign, and find out why.

What good looks like

Your main domain never sends a cold email, every sending domain passes SPF, DKIM and DMARC, and you have enough warmed inboxes for your volume at 30 a day each.

Mistakes to skip

• Sending from day one. Warmup takes two weeks, and skipping it burns the domain.
• Lookalike domains that don’t lead anywhere. Buyers check, and a dead domain looks like a scam.
• Buying more inboxes to fix a bad list. If bounces are high, more inboxes just spread the damage.