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SMTP OAuth2: Token Authentication for Email Clients
Learn how SMTP OAuth2 works, build XOAUTH2 safely, refresh tokens without duplicate sends, and interpret 235 and 535 replies.
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Build an email reply parser that decodes MIME first, preserves thread evidence, and treats quoted text and signatures as confidence-scored heuristics.
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Learn how forged envelope senders turn late bounces into backscatter, and how SMTP-time rejection, null reverse paths, and safe auto-responses stop it...
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Learn what queued, sent, accepted, delivered, displayed, delayed, and bounced mean, plus the evidence each status can and cannot support.
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Read SPF records left to right, understand include, ip4, mx, redirect, qualifiers, and count DNS-triggering terms before changing DNS.
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Compare email API vs SMTP for retries, idempotency, portability, events, TLS, and ambiguous handoffs before choosing an application transport.
Read article →Which DNS Records Does a Domain Need to Receive Email?
Learn which DNS records let a domain receive email, why SPF, DKIM, DMARC, PTR, and a website do not prove recipient reachability, and what to check.
Read article →Email Bombing Prevention: Stop Your Signup Form From Becoming an Amplifier
Stop signup and reset forms from amplifying email bombing with pre-send rate limits, recipient cooldowns, deduplication, and step-up challenges.
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