How do I know if it is my iSP blocking port 25 or my RH8 Firewall setting
 

I am having problems with port 25.

NMAP shows port 25 is open when I scan localhost
NMAP shows port 25 is close when I scan my public ip 216.232.47.51

FTP, HTTP, SSH, POP3 and IMAP is open

I tried setting the redhat-config-securitylevel however the secrity level always showing high on the graphical UI? I have tried to set it to none or medium then go back to UI and still the same. Restarting the server does not work.

Here are the IMAP scans:

Interesting ports on sony1 (127.0.0.1):
(The 1592 ports scanned but not shown below are in state: closed)
Port State Service
21/tcp open ftp
22/tcp open ssh
25/tcp open smtp
80/tcp open http
106/tcp open pop3pw
110/tcp open pop-3
143/tcp open imap2
443/tcp open https
6000/tcp open X11

Interesting ports on sony1.28c.net (216.232.47.51):
(The 1593 ports scanned but not shown below are in state: closed)
Port State Service
21/tcp open ftp
22/tcp open ssh
80/tcp open http
106/tcp open pop3pw
110/tcp open pop-3
143/tcp open imap2
443/tcp open https
6000/tcp open X11

Thanks
Lawrence

Still new to Linux. Tried shutting down IPTABLES but port 25 still closed :(

Post your iptables firewall rules, it's under /etc/sysconfig, and we'll see, ok.

Which file in /etc/sysconfig do you need? There are no files starting with ip*. As far as I know firewall is not running.


[root@sony1 init.d]# ./iptables status
Table: filter
Chain INPUT (policy ACCEPT)
target prot opt source destination

Chain FORWARD (policy ACCEPT)
target prot opt source destination

Chain OUTPUT (policy ACCEPT)
target prot opt source destination
[root@sony1 init.d]# ./ipchains status
bash: ./ipchains: No such file or directory

As far as I know firewall is not running.
Any box connected to a network should have a firewall running, especiall a public one. Please see the 1st thread in this forum, 2nd post for firewall HOWTO's, scripts etc.

It was hook up to the DMZ zone of the Sonicwall Firewall but I was trying to trouble shoot the port 25 problem. That why it is wide open.

I will take a look at your posts.. Thanks

if you want to know if its blocked by your isp you might just give them a call and ask them. Or just disable your firewall or flush all its rules(iptables -F) and run nmap again, if the port is still blocked is most likely that your isp has it blocked. I still think that the easiest way to find out is to call your isp and ask.Most isp's do block port 25 to prevent spam.

I have confirmed that ISP is not blocking any port. I also tried moving the server back into LAN and tried to telnet into linux box from another machine at port 25, however it is still unsucessful.

This server is a new install. Firewall is not running. :(

you might want to double check that since i have noticed that some isp representatives don't actually know if they are blocking ports. My isp use to be verizon dsl and they block ports 25 and 80 so i called them up to ask why, the rep told me and explaine why(mostly because of spam and virus). I got disconnected so i called again and another rep answered and he told me they didnt block any ports.

Check your /var/log/maillog file for any errors or hints. run netstat -a and look for the smtp entry. It should be in listening to smtp port (25). Mine looks like this:

Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address Foreign Address State

tcp 0 0 *:smtp *:* LISTEN

Roger.

I have found out there is a configuration item in /etc/mail/sendmail.mc that said to only listen to 127.0.0.1 (localhost). It shouldn't have been there, but it was.

Everything is working now. Thanks