OS Blog: Guides on Email Verification, Deliverability & Cold Outreach
Notes on email verification, deliverability, and lead-gen.
MX Lookup Explained: What MX Records Tell You About Email Deliverability
MX records control where email for a domain gets delivered. Learn how to read them, what priority means, and how to diagnose deliverability issues with a free MX lookup.
SPF, DKIM, DMARC: The 3-Record Setup That Stops Your Emails Landing in Spam
Gmail and Outlook now require SPF, DKIM, and DMARC for bulk senders. Here's what each record does, how to set them up, and how to verify they're actually working.
Catch-All Emails: What They Are and How to Verify Them Safely
Catch-all domains accept mail to any address — so SMTP verification can't prove a mailbox exists. Here's why catch-alls are risky, and how to verify them without burning your sender reputation.
Email Blacklist Check: How to Tell If Your Domain or IP Is Blocked
Sending domain on a blacklist? Here's how to check the major DNSBLs (Spamhaus, Barracuda, SORBS), what each one actually does, and how to get delisted.
How to Clean an Old Email List Before Reactivating It
A 6-month-old email list rots fast. Here's the 5-step process to re-clean dormant lists before you re-engage, without burning your sender reputation in the process.
Bulk Email Verification: How to Verify 10,000 Emails Fast
How bulk email verification works under the hood, what to expect from a 10,000-row CSV, and how to read the results without losing valid addresses in the noise.
How to Find a Business Owner's Email Address (2026 Guide)
A practical guide to finding a business owner or founder's email — name research, pattern guessing, real-time SMTP verification, and rescuing risky catch-all addresses.
How to Verify Email Addresses (The 2026 Operator Guide)
A practical guide to verifying email addresses for cold outreach: syntax checks, SMTP verification, catch-all handling, and step-by-step CSV cleanup.
What a Typical Email Verification Run Actually Returns
See exactly what an email verification run returns: real status breakdowns, CSV layout, and what to do with each result. 200 free credits to try it.