Something that isin't mentioned at all (as far as I can tell) about greylisting is that people sending legit mail to a greylist receiver will get a message telling them that their message wasn't delivered and that the system will keep trying to deliver it (etc etc). Messages like this usually cause consternation, worry and confusion on the part of most people, and every effort should be made to not force known-good sending MTA's through a greylist challenge.
Hence my question, which is this:
Once a sending MTA has passed a greylist challenge, why isin't it automatically white-listed (by it's IP address) so that in the future all mail from it will be accepted?
Are there really instances where a sending MTA (located at a particular IP address) would pass a greylist challenge today, but fail it tommorrow, or next week?
Sum Guy Wrote:Something that isin't mentioned at all (as far as I can tell) about greylisting is that people sending legit mail to a greylist receiver will get a message telling them that their message wasn't delivered and that the system will keep trying to deliver it (etc etc).
no, most email servers do not generate these warnings, and even those that do can easily be configured not to.
Quote:Messages like this usually cause consternation, worry and confusion on the part of most people, and every effort should be made to not force known-good sending MTA's through a greylist challenge.
Hence my question, which is this:
Once a sending MTA has passed a greylist challenge, why isin't it automatically white-listed (by it's IP address) so that in the future all mail from it will be accepted?
uh... have you ever actually used greylisting? that is exactly how it does work. only the first message from a particular source is greylisted, and only for a small amount of time. This is kind of like the whole idea of greylisting.
Quote:Are there really instances where a sending MTA (located at a particular IP address) would pass a greylist challenge today, but fail it tommorrow, or next week?
There is no "greylist challenge". Your server (if it is properly configured) will simply resend the message and the greylisting server will accept it and every future message.
you seem a bit confused about what greylisting is and how it works. are you confusing greylisting with some sort of authenticated sender or other spam fighting technique?
Sum Guy Wrote:Something that isin't mentioned at all (as far as I can tell) about greylisting is that people sending legit mail to a greylist receiver will get a message telling them that their message wasn't delivered and that the system will keep trying to deliver it (etc etc). Messages like this usually cause consternation, worry and confusion on the part of most people, and every effort should be made to not force known-good sending MTA's through a greylist challenge.
I think typically a greylisting delay is between 5 and 25 minutes, while the "delayed delivery" warning is typically 4 hours. I've only seen such warnings when there has been a real network outage.