Guides
Practical, specific answers on email verification and deliverability: what the checks actually do, what the results mean, and what to do with them. Written by the people who built the Spaw pipeline.
- Disposable email domains and how detection works
Temporary inboxes live minutes. How the open disposable-domain list is built, why matching on MX hosts catches new burners, and what Spaw returns for one.
2026-09-03
- Email bounce rate benchmarks and what "acceptable" means
Published averages put hard bounces near 0.2% and soft bounces under 1% for opted-in lists. What mailbox providers enforce, and how to set your own target.
2026-09-03
- Email list cleaning checklist before a campaign
Ten steps in order: normalize and dedupe, import known bounces, verify in bulk, segment by verdict, authenticate, warm up, then keep it clean with monitors.
2026-09-03
- How Spaw computes the risk score
The risk score is a sum of published weights over documented flags, capped at 100, with undeliverable fixed at 100. Every weight, thresholds, examples.
2026-09-03
- How to verify an email address without sending an email
Parse the address, resolve the domain's mail servers, then ask the server about the mailbox in an SMTP handshake that ends before any message is sent.
2026-09-03
- Role-based email addresses and how to treat them
info@, support@, billing@ and about a thousand more belong to a function, not a person. How Spaw detects them, why senders flag them, and when to keep them.
2026-09-03
- SMTP bounce codes explained, from 550 5.1.1 to 421 4.7.0
What each SMTP reply and enhanced status code means, which are hard bounces, and how a verification handshake maps them to smtp_reason values.
2026-09-03
- SPF, DKIM and DMARC for developers
What each record proves, what it looks like in DNS, how receivers combine them, and what Gmail and Yahoo require from bulk senders since 2024.
2026-09-03
- What is a catch-all email address, and how should you handle it?
A catch-all domain accepts mail for every address, so no handshake can confirm one mailbox. What Spaw reports, how the confidence score works, when to send.
2026-09-03
- Why an email validation regex is not enough
A regex only rejects the impossible. It cannot say whether the domain accepts mail, the mailbox exists, or the address is a burner. What to run after it.
2026-09-03