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Insights and war stories from the inbox trenches.

AI coding subscriptions are cheap now, and email verification is why the free tier has limits

Cline Pass sits near $2.12 for month one with a promo code. Behind every one of those promotions is an email gate, because a discount that anyone can farm is not a discount.

tmail TeamOctober 24, 2026

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ARC: how forwarded mail survives SPF without breaking DMARC

tmail TeamOctober 24, 2026

Bot protection meets email verification: where Turnstile sits in a signup funnel

tmail TeamOctober 24, 2026

Building email testing into CI without the flake

tmail TeamOctober 24, 2026

Explore topics.

All 19 articles, everything we have learned about throwaway inboxes, deliverability, and signup automation.

OTP extraction from email: why regex keeps failing and what to parse instead

Pulling a verification code out of a message looks like a regex problem. It is a parsing problem, and the difference shows up the first time a template changes.

tmail TeamOctober 24, 2026

Smoke-testing a signup flow without creating production accounts

Testing onboarding usually means either touching production or skipping the test. A disposable address plus a scoped test key gets you the real flow with none of the real accounts.

tmail TeamOctober 24, 2026

SMTP retry timers vs test suites: why your pipeline can never wait long enough

Real mail delivery failure is a temporary state handled over hours or days. Test suites budget seconds. Understanding the gap explains which failures you can test and which you can only observe.

tmail TeamOctober 24, 2026

The SMTP limits that quietly break your email tests

RFC 5321 puts hard numbers on command lines, local parts, and domains. Test suites violate them constantly, then blame the mail server when delivery fails.

tmail TeamOctober 24, 2026

Mailpit, MailHog, or Maildev: choosing a local SMTP sink in 2026

MailHog has 16,191 stars and has not shipped since 2020. Mailpit has 10,738 and shipped four days ago. Picking the wrong one costs you a migration later.

tmail TeamOctober 24, 2026

SPF's 10-lookup limit: why your mail vanishes and nobody tells you

RFC 7208 caps SPF evaluation at 10 DNS-lookup terms. Cross it and the result is permerror, which most receivers read as 'no SPF at all'. The fix is subtraction, not addition.

tmail TeamOctober 24, 2026