The cold email infrastructure checklist

Cold email still works — but only if it reaches the inbox. Mailbox providers have become much stricter about who gets delivered, and a single bad campaign from your main domain can affect every email your company sends. This checklist covers the infrastructure that should be in place before the first send.

1. Protect your primary domain

Never run cold outreach from the domain your team uses for customers, invoices and hiring. Instead:

• Register a few secondary domains that are clearly related to your brand (for example, variations of your company name).
• Redirect them to your main website so prospects who check land somewhere familiar.
• Spread sending across several domains and inboxes so no single one carries all the volume.

2. Authenticate every domain

Each sending domain needs:

• SPF — lists which servers are allowed to send on behalf of the domain.
• DKIM — cryptographically signs your messages so they can’t be tampered with.
• DMARC — tells receivers what to do when SPF or DKIM fail, and gives you reports.

Since 2024, Google and Yahoo have required bulk senders to authenticate with SPF, DKIM and DMARC and to keep spam complaint rates low — Google’s guidance is to stay below 0.3%, ideally under 0.1%. Even if you don’t hit bulk volumes, meeting these standards is the baseline for good deliverability.

3. Set up real inboxes

Use proper mailboxes on a reputable provider, each with a real sender name, profile photo and signature. Avoid sending cold email from shared marketing platforms built for newsletters.

4. Warm up before you send

New domains and inboxes have no reputation. Warm them up gradually over a few weeks before launching campaigns, and keep warm-up running in the background afterwards. Once live, ramp volume slowly — a modest daily cap per inbox is far safer than a big first-day blast.

5. Clean data in, clean reputation out

Bounces are one of the fastest ways to damage a domain. Before any list enters a sequence:

• Verify every email address.
• Remove role accounts (info@, sales@) unless you have a good reason to include them.
• Exclude anyone who has opted out in the past.

6. Write like a human, for one person

Deliverability isn’t only technical. Messages that are short, relevant and plain-text-like tend to perform better with both filters and humans:

• Keep links and images to a minimum, especially in the first touch.
• Avoid heavy tracking and link shorteners.
• Make it easy to say no — and honor it immediately.

7. Monitor continuously

Infrastructure isn’t set-and-forget. Track, per domain and inbox:

• Bounce rate and spam complaints
• Inbox placement tests
• Reply rates by segment (a sudden drop often signals a deliverability issue before anything else does)

Rotate out any inbox that starts to struggle, fix the cause, and only then bring it back.

The short version

Separate domains, full authentication, gradual warm-up, verified data, human copy and constant monitoring. Get those right and your messaging finally gets the chance to do its job.