From: Victor Duchovni (Victor.DuchovniMorganStanley.com)
Date: Mon Sep 24 2007 - 21:51:31 CDT

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On Mon, Sep 24, 2007 at 07:06:40PM -0700, Rick Kunkel wrote:

> Sep 24 11:03:03 valinor postfix/smtpd[29377]: connect from
> seadsl-d-X.X.X.X.dsl.w-link.net[X.X.X.X]

Client connects.

> Sep 24 11:03:03 valinor postfix/smtpd[29377]: 37778FEBF9:
> client=seadsl-d-X.X.X.X.dsl.w-link.net[X.X.X.X]

A "RCPT TO:" command is accepted from the client and a queue file is
created to hold a new message envelope (and any subsequent data).

> Sep 24 11:03:03 valinor postfix/smtpd[29377]: 9CE88FEBF6:
> client=seadsl-d-X.X.X.X.dsl.w-link.net[X.X.X.X]

The previous transaction is most likely aborted via "RSET", and a new
transaction is started, this time a new "RCPT TO:" is accepted, ...

> Sep 24 11:03:06 valinor postfix/smtpd[29377]: 1F106FEBF6:
> client=seadsl-d-X.X.X.X.dsl.w-link.net[X.X.X.X]
>
> .
> . (about 116 more of this kind of thing)
> .

Lather, rinse, repeat...

> Sep 24 11:04:22 valinor postfix/smtpd[29377]: too many errors after RSET
> from seadsl-d-X.X.X.X.dsl.w-link.net[X.X.X.X]

Without any actual deliveries (did any of the queue ids in question
have postfix/cleanup or postfix/qmgr log entries), the long recipient
verification run (somewhat akin to a dictionary attack) eventually
leads to Postfix refusing further service.

Is Outlook (or a mail-merge plugin for Outlook) attempting some form of
email address verification prior to message transmission?

--
        Viktor.

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