On 15/02/2012 8:19 PM, Tim Connors wrote:
On Wed, 15 Feb 2012, Andrew McGlashan wrote:
On 15/02/2012 7:20 PM, Matthew Cengia wrote:
On 2012-02-15 19:03, Jason White wrote: [...]
based on a few minutes of reading, I couldn't find anything in RFC2821 that would require it.
And it's odd that Andrew would claim otherwise. It's not even a sane thing to put into the relevant standards.
Sure it is ;-) -- at least I think so... or at minimum consider it.
Perhaps the standard needs to be amended to ensure that if there is 451 or other TEMPORARY type error that the mail server should be able to expect further communication from the same sending SMTP host using the original IP if possible -- this would help significantly with greylisting.
And make it impossible to implement certain types of highly available MTA clusters. What happens when the MTA that sent out the email that you have greylisted, then crashes before it gets a chance to try again? Should no other MTA in the cluster be allowed to pull the message off the spool on shared storage and retry itself?
Large MTA clusters seem to have enough issues of their own .... how many Big Pong emails have gone missing or been delayed for extraordinary amounts of time?
The specific implementation of your greylisting is not of concern to people running big MTAs. There are many implementations of greylisting and spam filtering in general. Pick another one that works for the kinds of email from the kinds of people you expect to receive.
Greylisting works on tuples, one part of the tuple is the originating IP address. If you have a bunch of servers with different public facing IP addresses retrying the same email, then that makes it a much greater workload to finally offload the email to the recipient server. If you want to deliver and finish with the email more quickly, then resend it from the same original IP address when you can. If that server dies, then offload it to another server, but don't try to send it from a zillion addresses and making the problem so much greater. -- Kind Regards AndrewM