I just installed a Linksys wired router between my e-mail/web server and the Internet and I am now unable to send e-mail. I am using Sendmail as the MTA and Kmail as the UA. When I send a message it says Sendmail exited unexpectedly.

The router also seems to be preventing access to hotmail.

I have set the port forwarding and triggering as follows:

Port 25 SMTP
Port 53 DNS
Port 80 HTTP
Port 110 POP3

I am using SuSe 8.1. Receiving e-mails from outside the domain works well and the web site can also be viewed from the Internet and inside the domain.

Any help would be appreciated.

Thanks.

There is a possability that this is a problem with the Maximum Transfer Unit (MTU) setting. It is the most data that can be sent in one packet. You haven't by any chance just got ADSL and are located in the UK?

I experienced this problem when we first got ADSL. It seems that BT (a company who provides a large portion of the UKs telecoms hardware) has some of the MTU settings on its routers set to 1458, whereas the default is 1500. This means (i think) that the last 42 bytes of data get trimmed off, resulting an quite a maimed and useless packet. This is only a problem when contacting certain sites as it depends on what hardware you go through. The most notable of these sites is..... hotmail.com.

Now, even if you are not in the UK this could still be an issue. You should probably check your router's MTU setting (if possible) as well as your MTU setting. To check your MTU value you can do (as root):
ifconfig
This will list your network settings where you should see your MTU value. You can change your MTU value using:
ifconfig eth0 mtu 1500
(you may need to change eth0 to the interface that you use for Internet access). You could try reducing the 1500 value until your connection works (which it hopefully will).

I'm not sure if you will need to restart your network adaptors or now. I could do with someone out there how has more experience with this sort of thing confirming this for me. I think I have got the theory behind it mostly correct.


Good luck!


Radam

Well, that fixed the Hotmail problem right off the bat. However, I still cannot send mail from my server. I had the MTU setting to automatic. Now it is at 1458.

I am in the U.S.

Before I installed the router, I had my computer connected directly to the modem. I was able to send e-mails with that configuration. I have a static IP using what I believe is SDSL. The cable to the wall only has two pins.

Thnks for the help. I would have never done that in a million years.

Hi LSEmpyrean,

I'm pleased that solved at least one problem. Sadly though, I am no email expert, lest of all sendmail. Here are the two things I can think of:
1 - Try sending mail without using your install sendmail. Could you send mail directly through your ISP's mail servers. If this still gives you errors then it will probably be a connection problem. If so you may have the infinite joy of contact your ISP's support desk, as this would lie in their domain.

2 - Check through the various log files (not that I know where they are kept) for any little errors.

Sorry, but those are the only things I can think of. You may want to start a new thread to entice any sendmail experts there are that lurk on these forums.

Best of luck with solving the problem though!

Radam

What port does Sendmail send out on? I don't think it's any of the ports in your list and I assume all other traffic is denied?

Best regards,

The problem now seems to be fixed. I changed the NAT and the ports and it suddenly works. Thanks for the help.