SMTP

[rub3x]

Erm is there something I am doing wrong? Nmap says 25 is open. My ISP filtered 25 a while ago but I called and they said they would unfilter it. How can I tell if it still filtered? I can telnet to remote SMTP server and send mail remotly. This is what I did.
rub3x@Force:~$ telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 Force.Knowledge ESMTP Sendmail 8.13.4/8.13.3; Sun, 19 Jun 2005 19:21:32 -0900
MAIL FROM:th3rub3x@gmail.com
250 2.1.0 th3rub3x@gmail.com... Sender ok
RCPT TO:th3rub3x@gmail.com
250 2.1.5 th3rub3x@gmail.com... Recipient ok
DATA
354 Enter mail, end with "." on a line by itself
SUBJECT:HELLO
HELLO
.
250 2.0.0 j5K4LWCA010538 Message accepted for delivery

It just hangs after it says accepted for devilvery. I get no new mail.

[mattlso]

The only way to tell is to scan it remotely, or try sending an email remotely to your system. Open a free webmail and send an email to your box, if it works, its open!

There is a web based port scanner I sometimes use at:

http://www.t1shopper.com/tools/port-scanner/

Regards

[T40Slack]

Are you trying to use your server as a SMTP server? If so, is there an MX record somewhere on the Internet that lists your machine as a valid SMTP source for a domain?

Some servers filter based on matching the source e-mail domain with the domain of the server the mail is coming from. So if your domain does not match your source IP, the receiving server drops the Mail message and counts it as SPAM.

But like was mentioned above, try looking at the transaction between the servers by using a scanner of some sort (or even TCPDump, if you can read and understand the output)