topic Re: telnet to port25 using other machine in Operating System - Linux

telnet to port25 using other machine

ping1234 — Thu, 17 Apr 2003 03:23:07 GMT

I can telnet to port25 at the server. But I can't telnet to port25 at other machine, what's wrong with my setting?

Is this also the reason why I can't use outlook at other machine to send mail with my linux mail server? If this is not the reason, what's going wrong?

Please help.

Re: telnet to port25 using other machine

Sergejs Svitnevs — Thu, 17 Apr 2003 05:30:41 GMT

You should then examine the sendmail log (/var/log/messages, /var/log/secure) and iptables log
for messages that will indicate the nature of the problem.

RELEASE NOTES:
By default, sendmail does not accept network connections from any host other than the local computer. If you want to configure sendmail as a server for other clients, please edit /etc/mail/sendmail.mc and change DAEMON_OPTIONS to also listen on network devices, or comment out this option all together. You will need to regenerate /etc/sendmail.cf.

SUSE:
On default SuSE sendmail is configured to listen to 127.0.0.1 only. To change this, set "SMTPD LISTEN REMOTE" to "yes" in
/etc/sysconfig/mail.

Regards,
Sergejs

Re: telnet to port25 using other machine

Stuart Browne — Thu, 17 Apr 2003 05:32:12 GMT

You've just started trying to use SMTP (Sendmail) on a RH Linux box after a new install?

You'll need to check to see if Sendmail is listening on anything bar the local host:

netstat -ntlp | grep sendmail

If you have a line that looks like:

tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN /sendmail: acc

Then this is the case.

To fix this, you need to modify (regenerate) your 'sendmail.cf' file. If it's a RH system, you'll have an '/etc/mail/sendmail.mc' file. You'll have a line that reads something like this:

DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA')

Insert the 3 letters 'dnl' infront of this line, then re-generate your sendmail cf using the the following:

m4 /etc/mail/sendmail.cf > /etc/sendmail.cf

(NOTE: This is for a RH7 without an eratta sendmail. Otherwise, it'll be /etc/mail/sendmail.cf).

After a restart of sendmail, the line from the netstat command should show '0.0.0.0:25'.

Hope this helps.

Re: telnet to port25 using other machine

Jerome Henry — Thu, 17 Apr 2003 12:02:52 GMT

following your other board, I feel it's just the same trouble : your other machines run sendmail, both for sending and receiving mails, before usually transfering to another program. If your machines are set up to send (then you see sendmail somewhere) but not to receive or relay, like the other time, then it is that your sendmail hasn't been configured for relaying.
If you want to do so (is it a goo idea on every machines, as usually users want to send & receive, not to relay), then follow the process suggested before, but be cautious on this necessity to set up relaying, which causes your machine to relay... who ? Be cautious on the definition of who you'll accept.
Yours.