Deliverability
Deliverability fundamentals
Why mail lands in spam, bounce handling, list hygiene and the engagement signals that move the needle.
The Gmail and Yahoo bulk sender rules: a 2026 checklist
What changed in February 2024, what was tightened in 2025, and the seven requirements you must meet if you send over 5,000 messages a day.
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Inbox placement testing: what seed tests can and cannot prove
Seed tests are useful diagnostics, but they do not replace reputation, engagement, and real recipient behavior.
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Bulk email validation CSV checklist
A practical checklist for uploading, validating, segmenting, and exporting CSV email lists without damaging sender reputation.
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How to check if your email will go to spam before launch
A launch checklist for testing real messages, sender authentication, DNS, headers, content, links, and recipient quality before a campaign or product email goes live.
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Why your emails land in spam
Beyond authentication: content patterns, IP reputation, and engagement signals that quietly route legitimate mail to junk folders.
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Bounces decoded: hard, soft, block, and how to handle each
What every SMTP bounce code actually means, which ones to retry, and the suppression rules that keep your reputation intact.
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Feedback loops (FBLs): how to know when recipients hit 'spam'
Every major receiver's FBL program, how to enroll, and the suppression discipline that turns complaints into long-term placement gains.
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List-Unsubscribe and one-click unsubscribe: the 2024 requirement
Gmail and Yahoo now require RFC 8058 one-click unsubscribe for bulk senders. Here are both header formats, the POST endpoint contract, and the gotchas that break it.
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Return-Path: where bounces actually go and why it matters
The Return-Path header tells receivers where to send bounce notifications. Get it wrong and you go blind to delivery failures. Here is the SPF, DMARC, and bounce-loop interaction.
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List hygiene: when to suppress, when to sunset, when to remove
The discipline that separates senders with 30% open rates from senders in spam: validating signups, sunsetting unengaged, and the four suppression categories you must track separately.
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Warming a new sending domain — a realistic 4-week schedule
Day-by-day volume targets, recipient selection, and the warning signs that mean you should slow down.
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Transactional vs marketing email — separate them or suffer
Why running both streams from the same domain is a deliverability liability and how to split them cleanly.
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