Re: Outbox traffic jam?

[Brian Stafford <brian stafford uklinux net>]

On Wed, 27 June 20:15 Scott Thomason wrote:
| SMTP servers are very common users of identd, I think they use it to
| put the true, supposedly unspoofed user-id in email headers.

The only place an MTA can put this information is in the Received:
header.  This is mainly for human consumption and is only ever examined
if there is a problem.

Knowing the user ID of a downstream MTA isn't much use in SMTP,
usually its just the userid the MTA runs as (not necessarily root).
Since the downstream MTA may already be a few hops along the delivery
path, this user ID is unrelated to any of the identities in the SMTP
envelope or the message headers (which the MTA is not allowed to
examine or process anyway).

An MTA will usually apply its relaying rules to the combination of
the MAIL FROM mailbox and the RCPT TO mailbox.  Neither of these
are likely to be related to the IP address of the previous or next
hops.  The userid of the MTA processes in the previous and next
hop are irrelevant.

| If everyone enacted firewall rules to simply drop identd packets,
| email all across the world would grind to a screeching halt waiting

| for tcp timeouts (instead of receiving an immediately obvious
| connection rejection).

I'm not convinced.  Or am I missing the point of something useful here?

Brian