SMTP error when connected to Belkin router

[CobaltWolf]

I have my home network set like this: DSL modem Thompson Speedtouch 530 (software release 4.2.7.16.0) connected to a Belkin Wireless G. Router F5D7230-4 (ver. 4002), and from there connected to two PCs.

This problem started like a month or two ago. Everything was fine before that. I'm not sure what I could have possibly changed to cause this issue. I've ruled out my software firewall (I uninstalled it to be sure). I also disabled NOD32 while sending to rule it out as well.

What happens is this: I am able to retrieve e-mails easily with either Thunderbird or Outlook Express. I'm even able to send e-mails that are EXTREMELY short (say, one that has only "Test Email" written in its body). However, if I try sending anything with a paragraph or longer, the e-mail program hangs, and I get an SMTP error:

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"Sending Message Failed: The message could not be sent because connecting to SMTP server [xxx.domain.name] failed. The server may be unavailable or is refusing SMTP connections. Please verify that your SMTP server is correct and try again, or else contact your network administrator."
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This happens with both of the PCs connected to the router.

Nevertheless, if I connect my Speedtouch DSL modem DIRECTLY into my PC, the e-mail is sent swiftly without any error message, as it should.

My knowledge of Networking and router settings is rather poor, so I don't know what I might've screwed up there. Any help (including pointing me to the right forum if this isn't it) would be immensely appreciated.

Regards,

Ed.


P.S. I'm adding the following data in case it's useful for you to help me better. First, to rule out my ISP, I tried to connect to the mailserver using telnet through port 25 (while using the Belkin router), and it apparently connected. Also, this is what I get from my ipconfig/all:

C:\Documents and Settings\Edwin>ipconfig/all

Windows IP Configuration

Host Name . . . . . . . . . . . . : phoenixblade
Primary Dns Suffix . . . . . . . :
Node Type . . . . . . . . . . . . : Unknown
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No
DNS Suffix Search List. . . . . . : Belkin

Ethernet adapter Local Area Connection 3:

Connection-specific DNS Suffix . : Belkin
Description . . . . . . . . . . . : NVIDIA nForce Networking Controller
Physical Address. . . . . . . . . : 00-11-D8-30-25-CB
Dhcp Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
IP Address. . . . . . . . . . . . : 192.168.2.3
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Default Gateway . . . . . . . . . : 192.168.2.1
DHCP Server . . . . . . . . . . . : 192.168.2.1
DNS Servers . . . . . . . . . . . : 10.0.0.138
Lease Obtained. . . . . . . . . . : Thursday, November 29, 2007 6:20:23 PM
Lease Expires . . . . . . . . . . : Monday, January 18, 2038 11:14:07 PM

 

[CobaltWolf]

Nevermind, I managed to work around the problem by setting up the Belkin as a brainless access point. E-mails can be sent now. Not elegant, and I lose the hardware firewall, but I write e-mail almost daily, so it's an uneasy compromise. The Linksys router I had before never gave me such problems.

I'll just set it up to router mode once again when I need those capabilities (since it is more roboust than the Speedtouch model I have).

Ed.