I have a customer using Redhat that is getting the following bounce from Comcast when root sends mail via sendmail. The actuall message is posted below so it gets throught but not clearly.


****************************email message************************************
The original message was received at Fri, 15 Feb 2008 09:32:52 -0500
from localhost.localdomain [127.0.0.1]

----- The following addresses had permanent fatal errors -----
<xxxxxxx@comcast.net>
(reason: 550 5.1.0 Invalid sender domain)

----- Transcript of session follows -----
... while talking to mx2.comcast.net.:
>>> MAIL From:<root@xxxxxx.localdomain> SIZE=323
<<< 550 5.1.0 Invalid sender domain
554 5.0.0 Service unavailable
unnamed

Encapsulated message
No Subject
From:
root <root@xxxxxxx1.localdomain>
To:
Date:
Today 9:32:51 am

Test message
End of encapsulated message
****************************email message************************************



I followed the steps at this site (stating the exact same problem): mpickering.homeip.net/phpwiki/HomePage/2004-06-24.html

But it still happens. I removed the edits suggested. Any ideas of what I am missing? Posted below is the sendmail.mc file. Any help is much appreciated!

****************************sendmail.mc************************************
FEATURE(`blacklist_recipients')dnl
EXPOSED_USER(`root')dnl
dnl #
dnl # The following causes sendmail to only listen on the IPv4 loopback address
dnl # 127.0.0.1 and not on any other network devices. Remove the loopback
dnl # address restriction to accept email from the internet or intranet.
dnl #
DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')dnl
dnl #
dnl # The following causes sendmail to additionally listen to port 587 for
dnl # mail from MUAs that authenticate. Roaming users who can't reach their
dnl # preferred sendmail daemon due to port 25 being blocked or redirected find
dnl # this useful.
dnl #
dnl DAEMON_OPTIONS(`Port=submission, Name=MSA, M=Ea')dnl
dnl #
dnl # The following causes sendmail to additionally listen to port 465, but
dnl # starting immediately in TLS mode upon connecting. Port 25 or 587 followed
dnl # by STARTTLS is preferred, but roaming clients using Outlook Express can't
dnl # do STARTTLS on ports other than 25. Mozilla Mail can ONLY use STARTTLS
dnl # and doesn't support the deprecated smtps; Evolution <1.1.1 uses smtps
dnl # when SSL is enabled-- STARTTLS support is available in version 1.1.1.
dnl #
dnl # For this to work your OpenSSL certificates must be configured.
dnl #
dnl DAEMON_OPTIONS(`Port=smtps, Name=TLSMTA, M=s')dnl
dnl #
dnl # The following causes sendmail to additionally listen on the IPv6 loopback
dnl # device. Remove the loopback address restriction listen to the network.
dnl #
dnl # NOTE: binding both IPv4 and IPv6 daemon to the same port requires
dnl # a kernel patch
dnl #
dnl DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6')dnl
dnl #
dnl # We strongly recommend not accepting unresolvable domains if you want to
dnl # protect yourself from spam. However, the laptop and users on computers
dnl # that do not have 24x7 DNS do need this.
dnl #
FEATURE(`accept_unresolvable_domains')dnl
dnl #
dnl FEATURE(`relay_based_on_MX')dnl
dnl #
dnl # Also accept email sent to "localhost.localdomain" as local email.
dnl #
LOCAL_DOMAIN(`localhost.localdomain')dnl
dnl #
dnl # The following example makes mail from this host and any additional
dnl # specified domains appear to be sent from mydomain.com
dnl #
dnl MASQUERADE_AS(`mydomain.com')dnl
dnl #
dnl # masquerade not just the headers, but the envelope as well
dnl #
dnl FEATURE(masquerade_envelope)dnl
dnl #
dnl # masquerade not just @mydomainalias.com, but @*.mydomainalias.com as well
dnl #
dnl FEATURE(masquerade_entire_domain)dnl
dnl #
dnl MASQUERADE_DOMAIN(localhost)dnl
dnl MASQUERADE_DOMAIN(localhost.localdomain)dnl
dnl MASQUERADE_DOMAIN(mydomainalias.com)dnl
dnl MASQUERADE_DOMAIN(mydomain.lan)dnl
MAILER(smtp)dnl
MAILER(procmail)dnl
"/etc/mail/sendmail.mc" 142L, 5759C

This portion explains it all:

The original message was received at Fri, 15 Feb 2008 09:32:52 -0500
from localhost.localdomain [127.0.0.1]

----- The following addresses had permanent fatal errors -----
<xxxxxxx@comcast.net>
(reason: 550 5.1.0 Invalid sender domain)

----- Transcript of session follows -----
... while talking to mx2.comcast.net.:
>>> MAIL From:<root@xxxxxx.localdomain> SIZE=323
<<< 550 5.1.0 Invalid sender domain
554 5.0.0 Service unavailable


It's saying that localhost.localdomain (the Red Hat computer)
received a message from itself. That message says it couldn't
deliver to xxxxxxx@comcast.net because of an invalid sender
domain. It then shows you the exact dialog that happened,
namely mx2.comcast.net says that xxxxxx.localdomain is not
a valid domain. Thus localhost.localdomain is sending
itself a 554 error, meaning that it can't deliver the message.

The fix for this is configure sendmail to know its proper
domain name or to have sendmail masquerade as its proper
domain name.

Any demos out there explaining how to do so? The one that seem to have the same issue (supplied as a link on the original post) did not seem to do the trick. Not too savvy with Linux however know enough to be dangerous.

Any help is appreciated.

Since you're running Red Hat, you can check out their
documentation at www.redhat.com/docs.

You could also open a support ticket if you know the
login for the account. Red Hat support is very good.

The problem is that the 'return address' for outgoing messages is generated
in the form localusername@localdomain, which is not a valid email address. That is what Comcast's smtp server is complaining about.

Since you don't have a permanent domain name (e.g. you just have a dynamic IP), there is no valid host which can return mail to arbitrary users on your system.

The solution is to map individual "fantasy" email addresses to corresponding real
email addresses somewhere (e.g. at gmail or your comcast email address). This can be
done using the 'generic' mapping feature of postfix.

Here's a link to how to do that on Ubuntu: http://ubuntuforums.org/showpost.php...81&postcount=4

On Redhat it will be the same principle. Good luck!