The 2026 cold email deliverability checklist

You can have perfect targeting and excellent copy and still fail, because a spam folder is indistinguishable from indifference. Deliverability is the least interesting part of outbound and the one most likely to quietly destroy a quarter.

Start with authentication. SPF, DKIM and a DMARC policy at least at quarantine are now effectively mandatory for bulk senders at Google and Microsoft. Send from a subdomain — go.yourcompany.com rather than yourcompany.com — so a bad campaign never damages the domain your invoices and password resets go out on.

Warm up new mailboxes for at least three weeks before real volume. Ramp from around ten sends a day to your target, and keep a hard per-mailbox ceiling once you get there. Two hundred a day per mailbox is aggressive; fifty is comfortable. More mailboxes beat more volume per mailbox every time.

List hygiene does more for your reputation than any copy change. Verify at send time rather than at import, suppress role addresses like info@ and sales@, and remove anyone who has not been confirmed in the last sixty days. A 2% bounce rate is the line most teams should treat as a ceiling.

On content: no tracking pixel on the first touch, no link in the first email, plain text formatting, and a real unsubscribe path. Each of those individually is worth a point or two of inbox placement, and together they are the difference between a campaign that works and one that never had a chance.

Finally, monitor rather than assume. Watch placement by provider, not just aggregate open rate, and treat a sudden drop at a single provider as an incident. SigmaGTM surfaces per-domain placement in the deliverability dashboard so the signal arrives before the quarter does.