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Telnet on port 25 refused, no firewalls in place, running sendmail 8.13

Posted on 2009-02-18
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Last Modified: 2013-12-17
Hello experts,
I run centos 5.2 (32 bit) which is RHEL 5 named mail-2 and am trying to setup a simple sendmail server. I have followed all the steps necessary, however, I cannot receive any mail through it outside of our corporate network (172.20.x.x). I can telnet to mail-2 with no problems on the inside from any of the machines on that range.
I have boxes outside to test if I can send an old fashioned telnet message over port 25 and it fails to connect to it.

telnet mail-2.mydomain.com 25 :: connection refused
but i opened up ssh and i can ssh (port 22) with no problems.
SELinux is disabled.

this box is on the dmz so it takes the firewall out of the equation. any help is appreciated.
----------------------------------------------------------------------
[root@mail-2 mail]# ps -ax | grep sendmail
 
 2101 ?        Ss     0:01 sendmail: accepting connections
 2109 ?        Ss     0:00 sendmail: Queue runner@01:00:00 for /var/spool/clientmqueue
 9905 ?        Ss     0:00 sendmail: ./n1HICd06009903 outbounds5.obsmtp.com.: client DATA status
 9907 pts/0    S+     0:00 grep sendmail
 
------------------------------------------------------------------
If you take a look at sendmail.mc, I commented out:
DaemonPortOptions=Port=smtp,Addr=x.x.x.x, Name=MTA as recommended to accept any address.
-------------------------------------------------------------------
[root@mail-2 mail]# netstat -nltp | grep -E "(:25|:110)"
tcp        0      0 0.0.0.0:25                  0.0.0.0:*                   LISTEN      2101/sendmail: acce
 
-------------------------------------------------------------------

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Question by:worpx
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by:fosiul01
fosiul01 earned 160 total points
ID: 23672119
i know what happneded!!!

you need to enable this ine in sendmail

dnl # DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl

then  type make command
then restart senmdail

it will work 100 %
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by:worpx
ID: 23672299
uncommented so it says:
DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl

and did make -C /etc/mail

restarted sendmail, still same problem.
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by:worpx
ID: 23673105
[root@mail-2 mail]# more sendmail.mc | grep DAEMON
dnl define(`confMAX_DAEMON_CHILDREN', `20')dnl
DAEMON_OPTIONS(`Port=smtp, Name=MTA')dnl
dnl DAEMON_OPTIONS(`Port=submission, Name=MSA, M=Ea')dnl
dnl DAEMON_OPTIONS(`Port=smtps, Name=TLSMTA, M=s')dnl
dnl DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6')dnl
dnl DAEMON_OPTIONS(`Name=MTA-v4, Family=inet, Name=MTA-v6, Family=inet6')

[root@mail-2 mail]# more sendmail.mc
divert(-1)dnl
dnl #
dnl # This is the sendmail macro config file for m4. If you make changes to
dnl # /etc/mail/sendmail.mc, you will need to regenerate the
dnl # /etc/mail/sendmail.cf file by confirming that the sendmail-cf package is
dnl # installed and then performing a
dnl #
dnl #     make -C /etc/mail
dnl #
include(`/usr/share/sendmail-cf/m4/cf.m4')dnl
VERSIONID(`setup for linux')dnl
OSTYPE(`linux')dnl
dnl #
dnl # Do not advertize sendmail version.
dnl #
dnl define(`confSMTP_LOGIN_MSG', `$j Sendmail; $b')dnl
dnl #
dnl # default logging level is 9, you might want to set it higher to
dnl # debug the configuration
dnl #
dnl define(`confLOG_LEVEL', `9')dnl
dnl #
dnl # Uncomment and edit the following line if your outgoing mail needs to
dnl # be sent out through an external mail server:
dnl #
RELAY_DOMAIN(`obsmtp.com')
RELAY_DOMAIN(`postini.com')
define(`SMART_HOST', `outbounds5.obsmtp.com')
dnl #
define(`confDEF_USER_ID', ``8:12'')dnl
dnl define(`confAUTO_REBUILD')dnl
define(`confTO_CONNECT', `1m')dnl
define(`confTRY_NULL_MX_LIST', `True')dnl
define(`confDONT_PROBE_INTERFACES', `True')dnl
define(`PROCMAIL_MAILER_PATH', `/usr/bin/procmail')dnl
define(`ALIAS_FILE', `/etc/aliases')dnl
define(`STATUS_FILE', `/var/log/mail/statistics')dnl
define(`UUCP_MAILER_MAX', `2000000')dnl
define(`confUSERDB_SPEC', `/etc/mail/userdb.db')dnl
define(`confPRIVACY_FLAGS', `authwarnings,novrfy,noexpn,restrictqrun')dnl
define(`confAUTH_OPTIONS', `A')dnl
dnl #
dnl # The following allows relaying if the user authenticates, and disallows
dnl # plaintext authentication (PLAIN/LOGIN) on non-TLS links
dnl #
dnl define(`confAUTH_OPTIONS', `A p')dnl
dnl #
dnl # PLAIN is the preferred plaintext authentication method and used by
dnl # Mozilla Mail and Evolution, though Outlook Express and other MUAs do
dnl # use LOGIN. Other mechanisms should be used if the connection is not
dnl # guaranteed secure.
dnl # Please remember that saslauthd needs to be running for AUTH.
dnl #
dnl TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN')dnl
dnl define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLA
IN')dnl
dnl #
dnl # Rudimentary information on creating certificates for sendmail TLS:
dnl #     cd /usr/share/ssl/certs; make sendmail.pem
dnl # Complete usage:
dnl #     make -C /usr/share/ssl/certs usage
dnl #
dnl define(`confCACERT_PATH', `/etc/pki/tls/certs')dnl
dnl define(`confCACERT', `/etc/pki/tls/certs/ca-bundle.crt')dnl
dnl define(`confSERVER_CERT', `/etc/pki/tls/certs/sendmail.pem')dnl
dnl define(`confSERVER_KEY', `/etc/pki/tls/certs/sendmail.pem')dnl
dnl #
dnl # This allows sendmail to use a keyfile that is shared with OpenLDAP's
dnl # slapd, which requires the file to be readble by group ldap
dnl #
dnl define(`confDONT_BLAME_SENDMAIL', `groupreadablekeyfile')dnl
dnl #
dnl define(`confTO_QUEUEWARN', `4h')dnl
dnl define(`confTO_QUEUERETURN', `5d')dnl
dnl define(`confQUEUE_LA', `12')dnl
dnl define(`confREFUSE_LA', `18')dnl
define(`confTO_IDENT', `0')dnl
dnl FEATURE(delay_checks)dnl
FEATURE(`no_default_msa', `dnl')dnl
FEATURE(`smrsh', `/usr/sbin/smrsh')dnl
FEATURE(`mailertable', `hash -o /etc/mail/mailertable.db')dnl
FEATURE(`virtusertable', `hash -o /etc/mail/virtusertable.db')dnl
FEATURE(redirect)dnl
FEATURE(always_add_domain)dnl
FEATURE(use_cw_file)dnl
FEATURE(use_ct_file)dnl
dnl #
dnl # The following limits the number of processes sendmail can fork to accept
dnl # incoming messages or process its message queues to 20.) sendmail refuses
dnl # to accept connections once it has reached its quota of child processes.
dnl #
dnl define(`confMAX_DAEMON_CHILDREN', `20')dnl
dnl #
dnl # Limits the number of new connections per second. This caps the overhead
dnl # incurred due to forking new sendmail processes. May be useful against
dnl # DoS attacks or barrages of spam. (As mentioned below, a per-IP address
dnl # limit would be useful but is not available as an option at this writing.)
dnl #
dnl define(`confCONNECTION_RATE_THROTTLE', `3')dnl
dnl #
dnl # The -t option will retry delivery if e.g. the user runs over his quota.
dnl #
FEATURE(local_procmail, `', `procmail -t -Y -a $h -d $u')dnl
FEATURE(`access_db', `hash -T<TMPF> -o /etc/mail/access.db')dnl
FEATURE(`blacklist_recipients')dnl
EXPOSED_USER(`root')dnl
dnl #
dnl # For using Cyrus-IMAPd as POP3/IMAP server through LMTP delivery uncomment
dnl # the following 2 definitions and activate below in the MAILER section the
dnl # cyrusv2 mailer.
dnl #
dnl define(`confLOCAL_MAILER', `cyrusv2')dnl
dnl define(`CYRUSV2_MAILER_ARGS', `FILE /var/lib/imap/socket/lmtp')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, 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 DAEMON_OPTIONS(`port=smtp,Addr=::1, Name=MTA-v6, Family=inet6')dnl
dnl #
dnl # enable both ipv6 and ipv4 in sendmail:
dnl #
dnl DAEMON_OPTIONS(`Name=MTA-v4, Family=inet, Name=MTA-v6, Family=inet6')
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
dnl MAILER(cyrusv2)dnl

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LVL 48

Assisted Solution

by:Tintin
Tintin earned 200 total points
ID: 23677664
I'm assuming that if you do

telnet mail-2.mydomain.com 25

on the box itself, you get a connection?

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Assisted Solution

by:Morne Lategan
Morne Lategan earned 80 total points
ID: 23677687
What does netstat -nlp | grep 25 give?
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Assisted Solution

by:Nopius
Nopius earned 80 total points
ID: 23678608
> this box is on the dmz so it takes the firewall out of the equation.

It doesn't. It's most probably an external firewall problem either on your border router/firewall or on ISP where your test machines located or on your ISP.

To find out where exactly packets stop, try to use tcptraceroute from the remote machine.
 http://michael.toren.net/code/tcptraceroute/
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Author Comment

by:worpx
ID: 23680853
"on the box itself, you get a connection?" yes

[root@mail-2 mail]# netstat -nlp | grep 25
tcp        0      0 0.0.0.0:25                  0.0.0.0:*                   LISTEN      3183/sendmail: acce
unix  2      [ ACC ]     STREAM     LISTENING     5255   1986/acpid          /var/run/acpid.socket

"It doesn't. It's most probably an external firewall problem either on your border router/firewall or on ISP where your test machines located or on your ISP."
called ISP, they are not blocking any ports for us (especially 25 since we have 4 other mail servers). we have a dedicated fiber line with an entire range of ips. I've already looked at the other mail servers and everything is the same, so I can't figure out why I can't get a simple telnet over 25.
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Assisted Solution

by:fosiul01
fosiul01 earned 160 total points
ID: 23680878
Hi worpx its me again

you said , if you connect your Old mail server instead of the new one, you would be able to telnet right ??

in that case,
Can you connect the old mail server , replace the new one, and when its done , just tel me, i just want to see if you can telnet to your old mailserver or not

does it make sense ??
its the only way to find out if its your firewall or something to do with you Ip and Isp
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Author Comment

by:worpx
ID: 23681118
old server can telnet 25 with no problems. it is not a hardware firewall issue it is the box. i am 100% sure on that.
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Accepted Solution

by:
worpx earned 0 total points
ID: 23681522
I solved it!!
For reference, look at your sendmail.swp file; it had an old host-name and that was the entire problem. Shutdown sendmail, removed the swap, and start sendmail. Everything works great. Thanks for all the clues!
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