Email deliverability blog
Practical guides on verifying lists, reading bounces and keeping your emails out of spam.
Bounces
Email Bounce Codes Explained: What 550 5.1.1, 421, 5.7.26 and Other SMTP Errors Mean
How to read an SMTP bounce code, the difference between hard and soft bounces, and what to do about the most common errors from Gmail, Outlook and other servers.
· 6 min read
Cold email
How to Clean an Email List Before a Cold Email Campaign (Step by Step)
A practical process to verify and clean a cold email list: which addresses to remove, how to treat catch-all and unknown results, and how to keep bounces under 2%.
· 5 min read
Verification
What Is a Catch-All Email Address? How to Verify and Handle Accept-All Domains
Catch-all domains accept mail for any address, so no verifier can confirm the mailbox. Here is how they work, how to detect them and how to send to them safely.
· 4 min read
Deliverability
Gmail, Yahoo and Outlook Sender Requirements in 2026: The Complete Checklist
What Gmail, Yahoo and Microsoft Outlook require from email senders in 2026: SPF, DKIM, DMARC, spam rate limits and one-click unsubscribe, with a setup checklist.
· 6 min read