How to Set Up Cold Email Infrastructure in 2026
Last updated: February 2026 | 20 min read
Cold email infrastructure is the technical foundation that enables you to send outreach emails at scale while maintaining deliverability. This guide walks you through everything you need to set up professional cold email operations from scratch.
Infrastructure Overview
Cold email infrastructure consists of several interconnected components:
- Domains: Separate domains for cold email (protecting your main brand)
- Mailboxes: Email accounts on Google Workspace or Microsoft 365
- DNS Records: SPF, DKIM, DMARC for email authentication
- Warmup: Building sender reputation before sending at volume
- Sequencer: Software to automate sending (Instantly, SmartLead, etc.)
Key Principle: Never use your primary business domain for cold email. Create separate domains to isolate reputation risk.
Choosing and Setting Up Domains
Domain Selection Strategy
Choose domains that are similar to your main brand but clearly separate:
- Brand variations: tryacme.com, getacme.io, acmehq.com
- Product focus: acmemail.com, acmesales.io
- Avoid: Hyphens, numbers, very long names, obscure TLDs
Recommended TLDs
Stick to trusted top-level domains for better deliverability:
- Best: .com, .io, .co, .net
- Good: .org, country-specific (.de, .uk) for regional targeting
- Avoid: .info, .biz, .xyz, and cheap/spammy TLDs
How Many Domains?
The number of domains depends on your sending volume:
| Daily Volume | Recommended Domains | Mailboxes per Domain |
|---|---|---|
| 100-300 | 2-3 | 2-3 |
| 300-1000 | 5-10 | 2-3 |
| 1000-5000 | 15-30 | 2-3 |
| 5000+ | 50+ | 2-3 |
Email Providers: Google vs Microsoft
Google Workspace and Microsoft 365 are the two main providers for cold email. Both offer excellent deliverability when set up correctly.
Google Workspace
- Gmail infrastructure and reputation
- Familiar interface for most users
- Strong spam filtering (helps warmup)
- US/EU IP addresses
Microsoft 365
- Outlook infrastructure
- Enterprise trust factor
- Different IP pool for diversification
- Global data centers
Pro Tip: Diversify across both Google and Microsoft to spread reputation risk. A 60/40 or 50/50 split is common practice.
Mailbox Setup Best Practices
Mailbox Naming
Create realistic-looking email addresses that match your persona:
- Good: john.smith@acme.io, sarah.johnson@tryacme.com
- Avoid: sales@, info@, noreply@, generic names
- Use real-sounding first.last or first@ formats
- Match the persona to your target audience
Profile Completeness
Complete mailbox profiles appear more legitimate:
- Add a professional profile photo (avatar)
- Fill in first name, last name, job title
- Create an email signature with contact details
- Consider LinkedIn profiles that match your sender personas
DNS Configuration
Proper DNS configuration is critical for deliverability. You need:
- MX Records: Route email to your provider (Google or Microsoft)
- SPF Record: Authorize your sending servers
- DKIM Record: Enable email signing
- DMARC Record: Set policy for authentication failures
Read our complete DNS setup guide
Volume Planning
Plan your infrastructure based on daily sending targets:
- Each mailbox should send 30-50 emails/day maximum
- New mailboxes start at 10-20/day during warmup
- Spread sending across multiple mailboxes
- Account for warmup time (2-4 weeks per mailbox)
Volume Calculator Example
Target: 500 cold emails per day
- Mailboxes needed: 500 / 50 = 10 mailboxes minimum
- Domains needed: 10 / 3 = 3-4 domains
- Recommended: 15 mailboxes across 5 domains (buffer for warmup rotation)
Connecting to Sequencers
Cold email sequencers automate your outreach campaigns. Popular options include:
- Instantly: Popular for high-volume cold email
- SmartLead: Advanced warmup and sending features
- Saleshandy: Good for teams and sequences
- Apollo: Combined prospecting and sequencing
- Lemlist: Known for personalization features
See all supported integrations
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