sendmail accept all domains even if they are unresolvable

sneakz · 04-13-2011, 10:02 AM

Hi,

I have one problem. When I put mailfrom:<toto@test.toto.fr>, I get Sender ok.

# sendmail -bs
220 serveur ESMTP Sendmail 8.13.8/8.13.8/Submit; Wed, 13 Apr 2011 14:22:10 +0400
helo localhost
250 serveur Hello test@localhost, pleased to meet you
250 2.1.0 <test@test.toto.com>... Sender ok

The error should be "553 5.1.8 <test@test.toto.com>... Domain of sender address test@test.toto.com does not exist".

I am able to get the google.com to resolve.

$ host google.com
google.com has address 209.85.146.103
...

And host test.toto.com returns :

Host test.toto.com not found: 3(NXDOMAIN)

# cat /etc/mail/sendmail.mc |grep accept_unresolvable_domains
FEATURE(`accept_unresolvable_domains')dnl

How can I fix it ?

Thanks for the help.

amonamarth · 04-14-2011, 07:42 PM

- comment out this line:dnl #FEATURE(`accept_unresolvable_domains')dnl
- make -C /etc/mail
- service sendmail restart

sneakz · 04-16-2011, 02:59 AM

Hi,

Thx. The solution is to comment out this accept_unresolvable_domains feature to force sendmail to refuse unresolvable domain.

Quote:

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 #
dnl FEATURE(`accept_unresolvable_domains')dnl

All is fine.

When I accept unresolvable domain in MAIL FROM, there is an output difference between telnet and sendmail with -bs parameter :

Quote:

# telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 serveur ESMTP Sendmail 8.13.8/8.13.8; Sat, 16 Apr 2011 13:11:19 +0400
helo localhost
250 serveur Hello localhost.localdomain [127.0.0.1], pleased to meet you
MAIL FROM: <toto@test.toto.fr>
250 2.1.0 <toto@test.toto.fr>... Sender ok
quit
221 2.0.0 serveur closing connection
Connection closed by foreign host.

Quote:

# sendmail -bs
220 serveur ESMTP Sendmail 8.13.8/8.13.8/Submit; Sat, 16 Apr 2011 13:12:17 +0400
helo localhost
250 serveur Hello root@localhost, pleased to meet you
MAIL FROM: <toto@test.toto.fr>
553 5.1.8 <toto@test.toto.fr>... Domain of sender address toto@test.toto.fr does not exist
quit

Why ?

amonamarth · 04-19-2011, 08:47 PM

Maybe your DNS client/server can't resolve it?

Try
dig toto.fr