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13 articles tagged with SMTP.
A timeout tells you where the SMTP conversation stopped, and that narrows the cause fast. Here are the timeout stages, the four root causes worth checking, a ten-minute diagnostic sequence, and the production patterns that prevent recurrence.
Self-hosted server, dedicated IP, or shared relay? They are three different decisions and most teams pick the expensive one for a hypothetical problem. A side-by-side comparison, the five cases that justify dedicated infrastructure, and the hidden ops costs nobody scopes.
Email API rate limits come in four layers - request rate, sending quota, SMTP concurrency, and receiving-ISP throttling - and each returns a different error. This guide covers reading rate-limit headers, which responses to retry and which never to, backoff with jitter, queue architecture, and separating transactional from bulk traffic.
Email webhooks push delivery, bounce, click, and complaint events to your application in real time instead of making you poll an API. This guide covers the event types and how far to trust each one, payload structure, building an endpoint that acknowledges fast and processes async, signature verification, handling duplicates and out-of-order delivery, and automatic suppression.
At high volume, your mail queue decides whether password resets arrive in seconds or minutes. Here is how to separate traffic classes, throttle per destination, build a retry ladder with jitter, enforce idempotency, and monitor the metrics that matter.
A shared IP pools your sending reputation with other senders; a dedicated IP gives you an address nobody else uses. This guide compares both across reputation, warmup, volume thresholds, and risk — with a side-by-side table, a realistic warmup schedule, and the deliverability fixes that matter more than either choice.
A practical reference for SMTP error codes: how to read a reply in ten seconds, the difference between 4xx soft bounces and 5xx hard bounces, lookup tables for the codes you will actually hit, and fixes for the five that cause most real-world pain — plus the ports that quietly cause silent failures.
The nine transactional email templates every product needs, with copy examples for password resets, receipts, failed payments, and shipping notices. Includes a transactional vs. marketing comparison table, sending-stream separation advice, variable-naming rules, and a pre-launch QA checklist.
Personal inboxes cap you at a few hundred emails a day, business suites at a few thousand. Here is what every provider tier actually allows, the four separate limits that stop sends, how to size the volume you really need, and a warmup ramp for scaling without tripping spam filters.
Reverse DNS maps your sending IP back to a hostname via a PTR record, and receiving servers check it before they decide whether to trust you. Here is how PTR records work, what forward-confirmed reverse DNS proves, who controls the record, how to verify it in two minutes, and the mistakes that quietly cost you inbox placement.
Email throttling is a temporary rate limit from receiving mail servers, not a rejection. Learn how to spot it in your SMTP logs, tell it apart from a block, read the deferral codes, and fix it with per-domain pacing, sane retries, and a proper warm-up schedule.
SMTP uses ports 25, 465, 587, and 2525. Here's what each port does, how they handle encryption, and which one to use when sending email.
SMTP is the internet standard for sending email. This beginner's guide explains what SMTP does, how a message travels, and how it differs from IMAP and POP3.
