On 5/3/2014 9:48 PM, post...@nisny.com wrote: ... > I am clueless as to why telnet would receive a correct response but > Postfix not. > > I know see this is not necessarily a Postfix issue but not sure what the > next step would be, so if anyone can offer guidance it would be > appreciated.
The answer to your problem is in your first post: > We had some initial problems with some private blacklists and the new IP but > those were resolved. However, I had a curious problem sending mail to > icloud.com addresses... The problem is exclusive, as far as we know, to this Akamai hosted MX farm. Wietse is obviously correct. Your telnet sessions work because they are a single connection. When you allow Postfix to deliver, it is making parallel connections to the farm because sufficient mail is queued for domains at that MX farm. You have two options to resolve this: 1. Create relay transports for the problem domains and limit concurrency to those domains, until your sender reputation with Akamai has increased to the point they allow parallel deliveries. 2. Contact the Akamai hostmaster and inquire as to what that threshold is, and when you may expect to surpass it. This problem is not new. The list archives are littered with threads dealing with ISPs who limit concurrency or delivery rate of "fresh" IP addresses. Those threads also contain instructions on how to do what I describe above to limit Postfix concurrency. Cheers, Stan
