Cold email deliverability: SPF, DKIM, DMARC and warmup in plain words.

Three records, one bouncer

Three small settings on your domain tell inbox providers that your mail is really yours.

• SPF is the guest list. It names the servers allowed to send email for your domain.
• DKIM is the wax seal. It signs each message, so the receiver can check it came from you and wasn't changed on the way.
• DMARC is the instruction to the bouncer. It says what to do with mail that fails the first two checks, and where to send you reports.

Google requires the full set from bulk senders to Gmail, meaning about 5,000 or more messages a day. SPF and DKIM must pass, and a DMARC record must exist with at least the lightest policy, which is p=none. The domain in your From address must also line up with the SPF or DKIM domain. Marketing mail needs a one click unsubscribe too. Even if you send far less, set up all three. They are the first thing a filter looks at.

Keep cold email off your main domain

Your main domain carries your customer emails, your invoices and your team's inbox. A reputation problem there is expensive. Cold email should go out from separate sending domains, so that if one gets a bad name, your real business email never feels it.

Two cautions. The sending domains must honestly be yours, and point back to your real website, because the law requires accurate sender details. And you should own them, so they are yours if you change providers.

Warm up before you send

A brand new mailbox has no history, and inbox providers don't trust strangers. Warmup means sending a small amount of normal looking mail first and increasing slowly, so a track record exists before real campaigns begin. We warm domains for about 14 days before a campaign touches them. Rushing this is the most common way people burn a new domain in its first week.

Send like a person, not a broadcast

• Plain text. No banners, no heavy design, no attachments.
• Few links. One at most, and often none in the first email.
• No tracking pixels. They add hidden images that make mail look like marketing. See why open rates lie.
• Modest volume per mailbox. Spread sending across several mailboxes instead of pushing one hard.
• Clean lists. Every bounce counts against you, so verify addresses first.

Watch it every week

Deliverability breaks quietly. Nothing errors out, replies just dry up. Check inbox placement with tests, watch bounces and spam complaints, and use Google Postmaster Tools to see your domain's spam rate in Gmail. Google's line is below 0.1%, and never 0.3%. We check placement weekly, and the placement on our clients' campaigns sits around 98%.

Setup checklist

• Separate sending domains that honestly belong to you
• SPF set up on every sending domain
• DKIM signing turned on
• A DMARC record, at least p=none
• A working unsubscribe in every email
• About two weeks of warmup before real volume
• Plain text emails with few or no links
• Verified addresses only
• A weekly placement and complaint check

Questions people ask