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.
FYI, this is obsoleted by RFC5321 now (and updated by 5336).
Okay, well it doesn't appear to be part of the standards, but it is painful for greylisting. Although I can understand that one IP may become blocked or have issues, whilst an alternate (sending) IP might be fine. 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. Cheers -- Kind Regards AndrewM