summary: (2) @@domain as return address? (long)

From: Haohui Wang (
Date: Tue Sep 15 1998 - 13:17:44 CDT

I should have waited at least 3 days before summarize.
After receiving a few more emails, and communication
with postmaster at the other site, I believe this
is a result of early Sun 8.6 rewriting rules. I randomly
picked up a few emails in mqueue and they all contained
a 8.6 sendmail host after the email was originated from
Exchange or CC:mail hosts. There should be a patch from
Sun fixes this.

Thanks to everyone responded, including Rich Kulawiec,
Lee Boon Heong, Frank Cusack, David Rossman, and Todd Brune.

As David Rossman put it:

Actually, I believe this problem is misleading. It has to do
with the fact that exchange server sends back <> as the
return address for any Exchange Postmaster messages. It turns
out that this is actually valid in the RFC. You need to
modify your file to fix the problem. Here is the
modification I made. Sorry I didn't get it to you before you
created the summary.

# handle "from:<>" special case
#R$*<>$* $@@ turn into magic
R$*<>$* $@$n turn into

David Rossman
UNIX Systems Administrator E-Mail:
Odetics, Inc.
1515 S. Manchester Ave. Voice: (714) 780-7820
Anaheim, CA 92802-2907 FAX: (714) 780-7995

The following was forwarded to me by Lee Boon Heong,

                   Symptoms and Resolutions article 16228
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SRDB ID: 16228

SYNOPSIS: Mail bounces with "501 MAIL FROM: unrecognized address:


In an environment which has MS Mailexchanger or a cc:Mail gateway
which uses a Sun machine running Sendmail 8.6 as a Mailhost to send mail
to the Internet. Mail from the MS exchange/cc:Mail gateway for the
internet is relayed to the mailhost, which actaully delivers the mail.
The mail from the internet is accpeted on the mailhost and forwarded
to the MS exchanger/CC-mail gateway.

The post master on the mailhost would see the bounced messages with
error messages similar to the following example:

The original message was received at Thu, 29 May 1997 12:30:41 -0700
from artemis []

   ----- The following addresses had delivery problems -----
<> (unrecoverable error)

   ----- Transcript of session follows -----
... while talking to cc:
>>> MAIL From:<@@hermes>
<<< 501 MAIL FROM: unrecognized address: <@@hermes>
554 <>... Remote protocol error


If analyzed this mail turns out to be mail which has bounced from the
Internet (for any reason) and was on its way back to the MS
gateway via the mailhost. The MS Exchange/cc:Mail gateway does not want
to accept the mail as the "MAIL FORM:" address does not stick to the
standards. "@@hostname" is an illegal SMTP address. Sendmail does not
have a restriction on Sender's address. But other SMTP gateways, which
need to translate the address to their native address formats, are
strict on adhering to the SMTP address format would not accept the
in the "@@hostname" format.

What exactly is happening?

User with cc:Mail sends mail to internet, and due to one of the many
possible errors (user not found/host not found, etc) the message is
sent back to the sender (bounces back). When a message is sent back
its recipient`s address is replaced by the sender's address and the
senders address is erased (contains just "<>").

When the bounced message's sender's address goes through the
ruleset 3 and then 11 on the customer's mailgateway ( as it has
to forward it back to the cc:Mail gateway which is in the local
domain => mailer=ether) it is transformed to "@@mail-gateway-name".

@@anything is an illegal internet address. Sendmail is forgiving with
regards to the format of the sender's address. Had the receiving end
been a box running Sendmail, it does not bother about "@@mailhostname"
in the sender's address. But since the receiving end is a "cc:Mail
which is not so forgiving regarding the format to the sender's address,
conversion works only with addresses adhering to the Internet
mail addressing protocol.


Insert the following line in the "S11" rule set after the line
starting with "R$=D"

"R@ $@mailer_daemon<@$w> for @@hostname

After the insertion S11 looks like this.

R$*<@$+>$* $1<@$2>$3 already ok
R$=D $@$1<@$w> tack on my hostname
R@ $@mailer_daemon<@$w> for @@hostname problem`
R$+ $@$1<@$m> tack on my mbox hostname


PRODUCT AREA: Gen. Network
PRODUCT: Sendmail

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Haohui Wang
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