Deliverability & reputation
Mailbox providers decide where your message lands using authentication results, the reputation of the sending IP and domain, and how recipients react. These guides cover the checks that decide whether mail is accepted, the bulk-sender rules Gmail, Yahoo and Microsoft now enforce, and what to do when an IP lands on a blocklist.
- Gmail, Yahoo and Microsoft sender requirements, explainedupdated 26 October 2026
What Gmail, Yahoo and Outlook.com require from senders in 2026: authentication and alignment, reverse DNS, one-click unsubscribe and spam-rate limits.
- How to get off an email blocklist (DNSBL)updated 26 October 2026
How DNS blocklists work, how to tell which listings matter, how to find and stop the cause, and how delisting works at Spamhaus, SpamCop and Barracuda.
- How to read email headers: Received, Authentication-Results and DKIMupdated 26 October 2026
Where to find a message's full headers, how to read the Received chain, and how to interpret Authentication-Results and DKIM-Signature when mail fails.
- Reverse DNS (PTR) for mail servers: setup and FCrDNSupdated 26 October 2026
Why receivers require a PTR record on sending IPs, what forward-confirmed reverse DNS means, who can set the record, and how to fix 4.7.23 and 5.7.25 bounces.
- Why is my email going to spam? A diagnostic checklist for adminsupdated 26 October 2026
A step-by-step checklist for why legitimate mail lands in junk: authentication, alignment, IP and domain reputation, reverse DNS, content and list hygiene.