SPF Flattening: Fixing the 10 DNS Lookup Limit Without Losing Deliverability
SPF has a hard limit, defined in RFC 7208: a receiving server will process at most 10 DNS lookups ...
How to Get Delisted from Spamhaus, Barracuda and Other Blacklists
Mail that was delivering fine suddenly starts bouncing, or a receiving server's rejection message mentions a domain like zen.spamhaus.org ...
IP and Domain Warm-Up: A Day-by-Day Plan for New Mail Servers
A brand-new IP address or sending domain has zero history with mailbox providers — and no history reads as ...
Reverse DNS (PTR) Records and Email Deliverability: Setup and Troubleshooting
SPF, DKIM and DMARC all live in your domain's forward DNS zone, which you control directly. PTR records don't ...
DKIM Key Rotation Without Breaking Authentication: A Step-by-Step Plan
DKIM keys don't expire on their own, which is exactly why they get forgotten. Most domains publish one key ...
ARC Headers Explained: Fixing SPF/DKIM Failures on Forwarded Mail and Mailing Lists
Enforce DMARC and, sooner or later, someone reports that legitimate mail sent through a mailing list, a corporate forwarder, ...
How to Read DMARC Aggregate (RUA) and Forensic (RUF) Reports
The moment you publish a DMARC record with a rua tag, mailbox providers start emailing you gzipped XML reports ...
Google & Yahoo Bulk Sender Requirements: The Compliance Checklist
Google and Yahoo tightened the rules for anyone sending significant volume to Gmail and Yahoo Mail addresses. The headline ...
MTA-STS and TLS-RPT: Enforcing Encrypted Delivery Between Mail Servers
Standard SMTP negotiates encryption with STARTTLS — but STARTTLS is opportunistic. If an attacker on the network path strips ...
BIMI Explained: How to Get Your Logo Verified in Gmail and Yahoo Inboxes
Brand Indicators for Message Identification (BIMI) puts your logo next to your emails in the inbox — right where ...