Sending domain strategy

The first rule of sending cold email at volume: never do it from your primary domain. If your cold campaign damages a domain's reputation, your transactional and sales emails from that domain suffer too. The architecture that protects you: dedicated sending domains, with your brand domain completely separate.

The anti-pattern

"Let's send cold email from sam@yourcompany.com because it has credibility."

Two months later: your CEO's emails are landing in spam. Your customer onboarding emails go to promotions. Your domain reputation is wrecked. Fixing it takes months.

This happens to every team that doesn't separate sending domains. Don't be them.

The domain architecture

Primary domain

Your brand: yourcompany.com. Used for:

• Your website
• Transactional emails (signup, password reset)
• One-to-one business email (from known addresses, to known addresses)

This domain should never send cold outreach at volume.

Sending domains

Additional domains purchased specifically for cold email: yourcompany.io, getyourcompany.com, try-yourcompany.com, yourcompany-team.com, etc.

Each sending domain:

• Points to your brand (has a redirect to yourcompany.com, mentions "yourcompany" so recipients trust it)
• Has its own DNS setup (SPF, DKIM, DMARC)
• Hosts 1-5 mailboxes
• Sends at low volume per mailbox (20-50/day)

Why multiple domains

One domain hits a per-domain sending ceiling (~1000-2000 emails/day before reputation starts degrading). Multiple domains let you scale horizontally.

Example: you want to send 1000 emails/day. You could use:

• 1 domain with 30 mailboxes sending 30-35/day each
• 5 domains with 5 mailboxes each, sending 40/day
• 10 domains with 3 mailboxes each, sending 35/day

More domains = lower per-domain volume = better reputation = better deliverability. Cost: domain registration (usually $10-20/year each) and slightly more setup work.

Domain naming

Do

• Variations of your brand: getyourcompany.com, yourcompany.io, yourcompany-co.com
• Industry-relevant: yourcompanyhq.com
• Short, memorable
• Redirect to your main site when visited

Don't

• Completely unrelated names that look like spoofing
• Misspellings of your brand (looks deceptive)
• Hyphens and numbers that look spammy (your-company-2026.com)
• Free domains (.tk, .ml etc.), spam-tier from day one

The mailbox-per-domain ratio

Best practices in 2026:

• 2-5 mailboxes per domain
• 30-50 emails/day per mailbox
• 150-250 emails/day per domain (total)

Going above 500/day per domain accelerates reputation burn. Below 20/day per mailbox means you're paying for infrastructure you're not using.

Domain age matters

New domains are treated with suspicion for 2-4 weeks. Brand-new domains sending cold mail on day 1 get filtered aggressively.

Two patterns:

• Buy fresh, warm slowly: register domain, set up DNS, start warming mailboxes immediately but send cold volume only after 4+ weeks
• Buy aged domains: purchase domains that have been registered for 6+ months (with clean history). More expensive but ready faster

Most teams use fresh domains with proper warming. Aged domains are the exception for urgent launches.

Redirects and brand trust

When a prospect clicks your signature link or Googles the sending domain, they should land somewhere that looks legit. Minimum setup:

• Sending domain redirects to your main site (301 redirect)
• Or a minimal landing page at the sending domain explaining "this is [yourcompany]'s outbound domain, main site is at yourcompany.com"

A bare sending domain with no website is a red flag to sophisticated recipients.

Workspace vs individual inbox

Each sending domain needs email hosting. Two options:

Google Workspace

• $6-18/user/month
• High deliverability to Gmail recipients (sender reputation boost)
• Easy to configure
• Standard for most cold email operators

Microsoft 365

• $6-22/user/month
• Strong for Outlook recipients
• Sometimes required for enterprise-facing campaigns

Dedicated SMTP providers

(SendGrid, Mailgun, Amazon SES, Postmark)

• Much cheaper at scale
• Lower deliverability to Gmail for cold
• Not recommended as primary cold-email infrastructure
• Fine for transactional, bad for cold outreach

For cold email in 2026: use Google Workspace primarily, Microsoft 365 when targeting Outlook-heavy audiences.

The launch cost math

For a mid-sized cold operation targeting 1000-2000 emails/day:

• 10 domains × $15/year = $150/year
• 30 Google Workspace mailboxes × $6/month = $2,160/year
• Cold email tool (Instantly, Smartlead): $100-500/month
• Warming tool: $50-200/month (often bundled)
• Data (Apollo, Clay): $300-1000/month

Total: ~$800-2500/month for a full operation. The mailboxes are the biggest line item.

The subdomain question

Can you use subdomains (outbound.yourcompany.com) instead of separate root domains?

Technically yes, but subdomain reputation partially ties to root domain reputation. If outbound subdomain gets flagged, it can contaminate yourcompany.com's reputation. Use separate root domains instead.

The checklist for a new sending domain

1. Register the domain
2. Set up DNS (use Cloudflare or similar for fast propagation)
3. Add SPF, DKIM, DMARC records
4. Configure email host (Google Workspace / Microsoft 365)
5. Enable DKIM in the email host
6. Set up redirect to your main site
7. Create mailboxes
8. Start warming each mailbox
9. Wait 3-4 weeks before sending real volume
10. Monitor Postmaster Tools and mail-tester scores

Next: Inbox warming.