Webmail in DMZ can't connect to sendmail SMTP

[superjoe]

Hi everyone,

I currently have a problem setting up a webmail for an (old) existing pop3 mailserver with sendmail. Here are the facts:

The mail server is a Solaris 8 box with sendmail, providing SMTP and POP3, and in the LAN zone.
I've successfully set up the webmail on a test VM in the same LAN zone : Debian, Apache 2, and Afterlogic Webmail Lite. Everything worked fine.

Then, I used an existing Debian server in the DMZ zone to install the webmail.
All the ports forwarding and other firewall configuration are correct.
I'm able to retrieve my mails with the webmail, but I can't send anything since I can't connect to SMTP server.
Obviously, I suspected a mail relaying problem, and added the IP address of the webmail to /etc/mail/relay-domains and /etc/mail/access (then recompiled to access.db) on the sendmail box.
But I'm still not able to send any mails, and I can't telnet the sendmail box on port 25.

Has anyone an idea ?

Thanks !

[davidanand]

stop the firewall and try once ...if you are able to do so make a rule such that tcp and udp makes connections ... good look

[superjoe]

I already tried to stop the firewall on the DMZ Debian box, but it doesn't change anything. It still got
DebianBoxDMZ# telnet mailserverIP 25
Trying mailserverIP...
telnet: Unable to connect to remote host: Connection refused
(for port 110, it works as I said before)


And concerning the main company firewall that links the DMZ, LAN and external, it obviously can't be stopped, but I allowed bidirectionnal communication between the DMZ and LAN zone. On the mailserver, there is no firewall. That's why I think the problem is on the mailserver side, but for the moment I'm still tring to find out what's wrong.

[davidanand]

check that are you able to telnet inside the server ..I meant
try as telnet localhost 25

[superjoe]

Yes, of course it works.
The mail server is running since something like a decade. Since now, the users have to connect to the VPN go get their mails popped into their mail client.

I don't know if it helps, but the Sendmail version is 8.9.1b

[davidanand]

what about your imap ..is it running ?

[superjoe]

We don't have imap running. The mailserver is quite old and it was not intended to provide imap.

But, I noticed that inside the Debian server that runs the webmail, I can't telnet any server (including my ISP smtp) on port 25 except localhost. I got the same thing from any server in the DMZ.
This is strange, since the company main firewall (Smoothwall corporate) allows all traffic from DMZ to outside. I'm going to dig more on that.

[superjoe]

Problem solved.
It comes from a special feature in Smoothwall called "Transparent SMTP Relay" that catches any smtp connection from external interface. I don't understand why, but Smoothwall considers my DMZ servers as external one in this case.

[davidanand]

what web mail client you are using ...such as squril mail, round cube or horde ...?

[superjoe]

We are using Afterlogic Webmail lite, which is one of the rare webmail to have a (good) support of POP3 mailservers. Moreover, it's deadly simple to configure.