SMTP problem - Relaying denied

[Gina]

As of last night, our whole company (about 50 users) has been unabe to send email. All other services like WWW, POP3 Proxy, Telnet, FTP are operational - but not SMTP Proxy.

We are a registered user of Wingate version 6.0.3 and we have been using POP3 Proxy and SMTP Proxy Services for email for over 4 years without problems. The machine running Wingate Server is Win NT4 sp6.

I have not made any changes at all in the last few weeks in Gatekeeper, or anything at all on the machine or OS running Wingate server.

This is what happens if we try to send an email from one of the clients behind the gateway, or even from the Wingate Server itself:
the email error message returned says:
550 5.7.1 <myname@mydomain.com.au> ... Relaying denied. IP name lookup failed [#.#.#.#]
(where #.#.#.# is the IP address of the wingate server's external adapter; this is a fixed IP address assigned to us by Optus).

In the SMTP Proxy Service we always have 'Support outbound mail via ISP mail server' selected and filled in with the correct details. And the bindings and adapters look right and say status: started, on port 25. All users have rights to use this service.

I've tried the following to troubleshoot:
) disable and stop SMTP Proxy Service, then restart SMTP Proxy Service
) shut down and reboot the machine a few times
) shut down and reboot the machine and turn off ADSL modem and restart everything
) stopped wingate service, deleted the history files, restarted wingate service
) checked and experimented with Port Security

Eventually I disabled the SMTP Proxy Service, went to Services/Email and enabled Delivery of mail, and then started the the SMTP Service.

So this works in the interim, phew!, but i really want the SMTP Proxy Service to work as it always did - it's faster when it goes through the ISP's smtp server.

Before switching to the SMTP Service, i noticed in Port Security that there was no "Redirect" action for Port 25 for "LAN connections to internet" (but there were for the other ports: 21, 110, 80, 8010). Does this mean anything?

Also, is it possible that a VPN session could have affected the SMTP Proxy Service ? We are currently trialling Wingate VPN, and last night a remote client connecting to this Wingate Server, claimed that their VPN connection froze (?), and after they rebooted the remote client, they could reconnect to the VPN again but they couldn't reach the LAN PC behind the Wingate Server which they had earlier been connected to.

Your help will be greatly appreciated.
Gina

[Nev]

Hi Gina, probably irrelevant but in Email --> Receiving --> have you enabled 'Allow relay' from trusted / lan user?

If not so, maybe the Wingate PC lost this setting somehow?

Just disabled it here and had a similar response to that which you are seeing.

Hope this helps.

[Gina]

hi Nev,
i checked - 'Allow relay' from trusted / lan user was enabled.
but my aim was to get the system working with SMTP Proxy Server with 'Support outbound mail via ISP mail server' enabled.

i think what's happened here is the ISP has blocked us from using their SMTP server - and it's not a wingate problem at all! they'll deny it of course...

this morning i reverted to the SMTP Proxy Server settings and it all seems to be back to normal and working again. :-)

[Nev]

Oh good Gina, now that is interesting, one client I have cut over to ADSL six months ago, immediately two causes prohibited outbound mail.

1: The IP assigned was dynamic and with a small amount of digging I retrieved a DNSBL entry for this whole block of addresses available to the hosting ISP.

Long story made short we obtained a Static public IP and were immediately off the DNSBL. The local ISP, Telco alike would not admit but the static IP cleared the entry.

So far so good.

Still could not send any message over 4kb from any machine in the organisation, also server challenge responses were buggy to faulty.

2: Digging revealed the default MTU for the new connection in the modem [which I supplied from a quality Australian maker] was too high.

Moved PPPoA MTU down to 1460 and bingo all well now for months.

No more packet fragmentation, actually even much lower could be better, but let working systems alone if not broken.

ISP was unaware and Telco wouldn't comment!

Not sure if there is any useful information in the above for you but here's hoping.