Can't telnet port 25

**sh4ka** · 06-29-2011

Hello,

This is the problem:

1 webserver running postfix to send vbulletin email notifications. The problem is I need to monitor when it's up and when it's not, so.. configured nagios but it doesn't seem to be responding to network requests.

This is what I got:

Code:

~/home/nagios/libexec/check_smtp -H 11.11.11.110 -p 25
Connection refused
SMTP CRITICAL - 0.006 sec. response time|time=0.006173s;;;0.000000

So, started diggin a little bit and this is what I found:

Service is up and running:

Code:

~service postfix status
master (pid 2386) is running...

Code:

~fuser -v 25/tcp

                     USER        PID ACCESS COMMAND
25/tcp:              root       2386 F.... master
                     postfix    2451 F.... smtpd
                     postfix    2462 F.... smtpd

Code:

~nmap -p 25 localhost

Starting Nmap 4.11  at 2011-06-29 12:01 CDT
Interesting ports on localhost localdomain (127.0.0.1):
PORT   STATE SERVICE
25/tcp open  smtp

Nmap finished: 1 IP address (1 host up) scanned in 0.014 seconds

Firewall is down:

Code:

~csf -x
[  OK  ] lfd:[  OK  ]
Flushing chain `INPUT'
Flushing chain `FORWARD'
Flushing chain `OUTPUT'
Flushing chain `DSHIELD'
Flushing chain `INVALID'
Flushing chain `INVDROP'
Flushing chain `LOCALINPUT'
Flushing chain `LOCALOUTPUT'
Flushing chain `LOGDROPIN'
Flushing chain `LOGDROPOUT'
Flushing chain `SPAMHAUS'
Deleting chain `DSHIELD'
Deleting chain `INVALID'
Deleting chain `INVDROP'
Deleting chain `LOCALINPUT'
Deleting chain `LOCALOUTPUT'
Deleting chain `LOGDROPIN'
Deleting chain `LOGDROPOUT'
Deleting chain `SPAMHAUS'
csf and lfd have been disabled

~iptables -F
You have new mail in /var/spool/mail/root

And still can not reach port 25 telnetting from outside:

Code:

~telnet 11.11.11.110 25
Trying 11.11.11.110...
telnet: connect to address 11.11.11.110: Connection refused
telnet: Unable to connect to remote host: Connection refused
You have new mail in /var/spool/mail/root

From inside the server, it works great:

Code:

~telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.localdomain (127.0.0.1).
Escape character is '^]'.
220 monitoring.server.com ESMTP Postfix

Any idea what am I missing?

Thanks a lot!

**atreyu** · 06-29-2011

Just a guess, do you have tcp_wrappers configured? check /etc/hosts.deny

**thorn** · 07-07-2011

your system may be refusing telnet requests

telnet has security issues and should be avoided

try:

ssh -P 25 <user>@11.11.11.110

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Can't telnet port 25

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