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On Apr 8, 2005, at 5:25 AM, Arun Sankar wrote:
It is definately backward compatiable as there is a Extended SMTP header (NCC) that also needs to be in place for the NCC processing to proceed.
no, it is not, in at least two ways:
1. with existing MUAs and other processors that don't display or take the Ncc field into account, it creates a mistaken impression that the message was sent to recipients that the message was not actually sent to
2. because not all systems will support Ncc (either because they predated it, or because they think it's not a desirable feature) senders might send a message with the mistaken expectation that it will not be delivered to particular recipients.
this extension seems of marginal value. it can be used to attempt duplicate suppression, such as when a message arrives at a recipient's mailbox both directly and via a list - but it's better to just have duplicates suppressed at the recipient's message store. the other use that comes to mind is that people will be tempted to use it as a way to implement "send to everyone on this mailing list except that troublemaker Joe". while I sympathize with the desire to do that, it will work so unreliably in practice that it's better to not have the feature.
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