Email deliverability guides
Why email does not arrive and how to fix it: spam, SPF, DKIM and DMARC, confirmation emails, password resets and SMTP error codes, in plain words.
Why your emails go to spam (and how to fix it)
The real reasons emails land in spam, from domain authentication (SPF, DKIM and DMARC) to reputation and content, how to find out which one is yours and what to do about each.
Read the guideHow to set up SPF, DKIM and DMARC (with Cloudflare and registro.br)
What SPF, DKIM and DMARC are, the right record for each and the step by step on Cloudflare, registro.br and hPanel, with the most common mistakes and how to check that it works.
Read the guideConfirmation email not arriving (Supabase, Firebase, WordPress)
Why sign-up confirmation emails do not arrive, what to check first and how to fix it in Supabase Auth, Firebase Auth and WordPress, with your own SMTP and an authenticated domain.
Read the guidePassword reset email not arriving? Causes and fixes
The password reset email never arrived. How to tell whether the app sent it, the provider refused it or it went to spam, and the practices that make reset emails arrive every time.
Read the guideWhat is transactional email (and how to send it right)
What transactional email is, examples, how it differs from marketing email, why to keep the two apart, the privacy basics and what a good sending service needs to have.
Read the guideSMTP error codes explained: 550, 421, 552 and more
What each SMTP error code means (550 5.7.1, 550 5.1.1, 421, 451, 452, 552, 554, 5.7.26, 5.7.515...), whether the problem is yours or the recipient's, and what to do in each case.
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