I have this strange problem: I have a T1 line and when ever line has problems (connection drops) my pop3(ipop3d) and smpt(sendmail) server stops responding. My Outlook users ger error msg "connection timed out...."

anybody heard of this problem yet ?

Also from time to time my smtp server seems to frezze a little and when i run "ps -x" on my linux pc i see line "sendmail starup with : <ip address>"

Regards, PcHammer

Your mail servers may be hanging as they try to connect to your ISP but cannot since the line is down.

OK so u are saying that if my line goes down i can not make my sendmail accept mail ?

Regards, Pchammer

I would wonder if it is a problem with DNS. Do you run a DNS server for your domain? If not, sendmail may be trying to do a look up or reverse lookup for the connecting client and can't, so it hangs because it can't reach the name server.

I've had similar problems with servers that do NAT. If the T1 were to go down, the internal clients couldn't even telnet to the server. This was fixed by making the server authorative for 1.168.192.in-addr.arpa as well as a fake domain to go with the internal network numbers.

No i'm not running DNS but i have my domain registerd with my ISP so i think that this could be the problem. If my line goes down lookup can't find my domain.
What would be the easyest was to fix this ?

Regards, PcHammer

Set up bind to run. I'm not sure if you're having problems with internal PC with translated addresses, or real hosts with real IP addresses. If it's real addresses, set up bind to be a slave for your domain and your network. Set the master to your providers nameserver, call them to make sure you have authority to pull the records from their server, and you will have a functioning secondary server. If the T1 goes down, your server will still be able to lookup the ip addresses of the connecting host.

If it's internal PCs your having problems with, consider setting up bind to be authoritive for your internal network. In other words, make it authorative for your.domain.com and, say, 192.168.1.. You will have to create all the records from scratch, but it should solve your problems. If you make the server so it answeres for internal PCs, use the listen-on substatement in the options portion of the /etc/named.conf file:

options {
listen-on { 192.168.1.1 };
};

Replace 192.168.1.1 with the ip address of your internal NIC. This will prevent the rest of the world from doing DNS lookups on your external NIC and determining the position of your internal PCs.

Here is the link to the How-To: http://www.linux.org/docs/ldp/howto/DNS-HOWTO.html
It looks a whole lot more complicated than it really is. Another good source is a book published by O'Reilly called DNS and BIND.

If you have any questions, just ask!

-Mark