Technical Guidance

PTR mechanisms in SPF records

If PTR mechanisms are detected, the current diagnostic output is: Warning: PTR mechanisms SHOULD NOT be used and cannot be resolved using this diagnostic tool. What does the PTR mechanism mean?  When an email receiver gets a piece of email and the PTR mechanism is in the sender's SPF record, the receiver will look at…
9 October 2015

Brief history of email authentication

Email is huge (largest deployed application on the Internet?) and it takes a long time to change the fundamentals. 2003: First SPF draft 2004: First DomainKeys draft (predecessor to DKIM) 2006: First DKIM draft PayPal begins work with Yahoo on authentication-based model 2007: BITS Email Security Working Group publishes paper recommending TLS + SPF +…
5 October 2015


A user once asked: I can't seem to find the answer to this question anywhere on the Internet (it may just be me not fully understanding the standards), so I thought I'd ask you. If I have DMARC set up in my DNS (which I do) and also ADSP (also do), which one takes…
4 October 2015