I recently installed Kubuntu 12.04 and am having problems getting kmail (4.8.2) working properly. I can download messages from the POP server; but only if I DONT leave a copy of the messages on the server. When I try and send a message I get the following SMTP error:

"5.7.1 Relaying Denied IP Name possibly forged [204.xx.xxx.xxx]"

I've tried different email accounts and different SMTP servers, but always get the same error. Thunderbird works fine for two different accounts using either SMTP server, under both Windows XP and Kubuntu 12.04.  I tried adding the IP address in question to /etc/hosts but that didn't help either.

I'm almost certain the problem has to do with the way kmail/kde is sending my network information to the smtp server, but everything else regarding network traffic is working fine.

Out of curiousity, I connected an old computer running Kubuntu 8.04 and received the same error. What's odd is kmail worked fine on this computer for years at two different locations. At my previous house I was connected to the internet through a DSL modem (no router) with a static IP address. At my current location I had that machine temporarily connected to a DSL modem/router using DHCP. This fall our ISP installed fiber to the house and replaced the router, and now kmail won't work properly on either computer.



Reproducible: Always

Steps to Reproduce:
1.Set up an account in Kmail
2.Send a message
3.
Actual Results:  
The message didn't get sent but was instead put into the outbox folder, and the following error message was received:
Failed to transport message. Message sending failed since the following recipients were rejected by the server: myemail@kcnet.com (The server responded: "5.7.1 <myemail@kcnet.com>... Relaying denied. IP name possibly forged [204.XX.XXX.XXX]")

Expected Results:  
The mail should have gone through.

The SMTP server does not require authentication and doesn't support encryption, so every other mail client I've used has no problem sending messages.