Cold email deliverability in 2026: the setup checklist

Why deliverability got harder

In 2024 Google and Yahoo introduced firm rules for anyone sending in volume to their users: authenticate your mail, make unsubscribing easy and keep spam complaints very low. Microsoft followed with similar requirements for Outlook.com. Filters also lean heavily on engagement, so emails that nobody opens or answers drag down the reputation of the inbox that sent them.

None of that makes cold email impossible. It means the technical setup must be right, volumes must stay modest per inbox, and the content must be something people actually want to reply to.

1. Use separate sending domains

Never send cold email from your main business domain. If something goes wrong, you want the damage contained to a domain you can retire, not the one your invoices and client emails come from.

• Register a few lookalike domains, such as getyourbrand.co.uk or yourbrandhq.com. Keep them close enough to your brand that a prospect recognises you.
• Prefer common extensions such as .com and .co.uk. Unusual extensions can look less trustworthy to filters and people.
• Point each domain at your real website with a redirect, so anyone who checks it lands somewhere credible.
• Buy the domains in your company's name so you own them whatever happens.

2. Set up a small number of inboxes per domain

Spread volume across many inboxes rather than pushing one inbox hard. We typically use two inboxes per domain on Google Workspace, each with a real person's name, a profile photo and a simple signature. Keep daily cold volume per inbox low; the exact ceiling depends on the provider and the age of the inbox, so start conservatively and only increase once placement looks healthy.

3. Authenticate with SPF, DKIM and DMARC

These three DNS records tell receiving servers that you are allowed to send from the domain and that the message was not tampered with.

Also set up a custom tracking domain if your sending tool uses link or open tracking, so you are not sharing a reputation with every other customer of that tool. Many senders now switch open tracking off altogether, since the tracking pixel itself can count against you.

4. Warm up before you send

New inboxes have no reputation. Warm-up builds one by sending and receiving small volumes of normal-looking mail, gradually increasing over time. We warm every inbox for 14 days before any cold send, and keep a lower level of warm-up running in the background afterwards.

Warm-up is not a magic shield. It gives an inbox a fair start, but poor lists and spammy copy will undo it within days.

5. Verify every list

Bounces are one of the fastest ways to damage a sending reputation. Run every list through a verification tool and remove invalid addresses. Treat "catch-all" addresses (where the server accepts everything) with care: send to them in small batches and watch the bounce rate. Our guide to building a B2B lead list covers this step in more depth.

6. Write emails that look like normal email

• Plain text, no images, no attachments in the first email.
• One link at most, ideally none in the first message.
• Short: a few sentences that a person could have typed.
• Vary wording between messages so you are not sending thousands of identical emails.
• Avoid spam-trigger habits such as all-caps subject lines, exclamation marks and "free" offers.

For structure, see our five-line cold email framework.

7. Rotate and rest inboxes

Inboxes tire. Keep a pool of warmed spare inboxes ready, and rotate them in as active inboxes show signs of strain, such as falling reply rates or poor placement results. Rest the tired ones on warm-up only. This keeps volume steady without pushing any single inbox too hard.

8. Test placement regularly

Do not assume emails land in the inbox. Every 14 days, send test emails to seed accounts across Google, Microsoft and other providers and check whether they reach the primary inbox, promotions or spam. Pause any inbox that fails and investigate before resuming.

Watch these numbers weekly: bounce rate, spam complaints, reply rate and positive reply rate. A sudden drop in replies without a change in copy is usually a deliverability problem, not a messaging one.

The checklist in one place

1. Separate lookalike domains, owned by you, redirecting to your site.
2. Two inboxes per domain with real names, photos and signatures.
3. SPF, DKIM and DMARC all passing; custom tracking domain or tracking off.
4. 14 days of warm-up before cold sending.
5. Every address verified; catch-alls handled carefully.
6. Plain, short, varied copy with minimal links.
7. Spare inboxes warmed and ready to rotate in.
8. Placement tests every 14 days and weekly metric reviews.

Prefer not to manage all this? Our done-for-you cold email service runs every step for you.