Hard bounce vs soft bounce: what the difference means for you
A hard bounce is a permanent rejection (5xx), a soft bounce is temporary (4xx). What causes each, how ESPs handle them, and when a soft bounce should be treated as hard.
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Deliverability, explained.
Guides and research on email verification, bounce rates, catch-all domains, disposable addresses, list hygiene and sender reputation. Written by the people who run the engine.
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@SPF, DKIM and DMARC setup for senders: a plain-English guide
SPF, DKIM and DMARC prove your mail comes from your domain. Plain-English definitions, a comparison table, numbered setup steps with example records, and how to move DMARC from none to reject.
@Email bounce rate benchmarks by industry in 2026: what is normal?
Typical email bounce rates by industry in 2026, how to calculate yours, where the 2% danger line sits, and how much list verification moves the number.
@WordPress form spam: stop fake sign-ups with real-time validation
CAPTCHAs and honeypots test behaviour, not the address. Real-time email validation stops typos, disposable domains and dead mailboxes on WordPress forms, with plugin setup steps.
@Email verification API: what it is and how to integrate one
An email verification API checks an address over SMTP and returns a verdict your code can act on. Here is the request, the JSON response, and working examples in curl, Node.js and Python.
@MX records explained: how mail finds its way to a domain
An MX record names the servers that accept mail for a domain. We cover priority values, a sample dig output, what Google, Microsoft 365 and Proton records look like, null MX and what a broken MX means for verification.
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