Email & deliverability

• Email & deliverabilityNew Email address validation: what a regex can and cannot prove The four questions hiding inside « is this a valid email address », why there is no official regex and which one to use instead, the six legal addresses forms wrongly throw out, the three length limits worth hard-coding, the one DNS lookup that catches the commonest real mistake, why an SMTP probe answers yes to addresses that do not exist, the honest case for and against blocking disposable domains, and the confirmation loop that is the only check that proves anything. 14 Sept 202621 min readIntermediate
• Email & deliverabilityNew Email bounces: how to read one, and what each code means What a bounce actually is and the two very different moments it happens, the three parts of a delivery report and which line carries the reason, how to read a reply code and an enhanced status code, the dozen codes that account for almost every bounce anybody reads, what can and cannot bounce at a disposable address, the bounces that belong to the hour you point your own domain here, and why a report sometimes arrives for a message you never sent. 9 Sept 202622 min readBeginner
• Email & deliverabilityNew MX records explained: priority, lookups and what breaks What an MX record is and the four things it is not, reading one with dig, nslookup or host, what the preference number actually decides and why a backup host is not a second chance, the seven steps a sending server takes, what happens when there is no MX at all and what a null MX says instead, the six ways the record breaks, the single record that points a domain here, and why an hour is not long enough. 9 Sept 202618 min readBeginner
• Email & deliverability Email headers: how to read one, and what it proves What the header block is and how it differs from the SMTP envelope, where to open the raw source in the mail app you already use, how to read the Received chain from the bottom up, the four fields that all claim to be the sender, what a pass or a fail in Authentication-Results really means, the five things a header can never tell you, and what is left to check when the message landed at a disposable address. 5 Sept 202621 min readBeginner
• Email & deliverability SPF and DMARC for a receive-only domain: stop spoofing Why a domain that never sends can go straight to the strictest SPF and DMARC on day one, the three records in full, the DKIM one you publish empty, checking your work with dig, and the parked-domain advice that would silently break your inbox. 29 Aug 202619 min readIntermediate

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