Email Deliverability Checklist for Developers: SPF, DKIM, DMARC and Warm-Up

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The article offers a practical guide for developers who send email, whether transactional, marketing, or cold outreach, on getting messages into recipients' inboxes. It explains how SPF lists authorized sending servers in DNS, how DKIM adds a cryptographic signature to verify messages were not altered, and how DMARC combines both and sets a policy for failed checks, recommending starting with monitoring. It also advises gradually warming up new domains or IPs to avoid spam flags, and processing bounces and complaints, removing hard-bounced addresses promptly. Finally, it recommends content practices such as avoiding spam-like phrasing and including plain-text versions and unsubscribe links, plus free tools for monitoring reputation.

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