cannot connect to internet, worked before
 

RedHat Linux 8.0 setup for a mail server with sendmail. Nothing was modified and all of a sudden I cannot connect to the internet, I believe that is why email cannot be sent/received anymore as well (the BIG problem). HELP PLEASE!!
I can ping the firewall and router, cannot ping anything outside our LAN, outside cannot ping the mailserver by name or IP. I talked to our DNS folks and they say everything checks out on their side.

\etc\hosts is......
# Do not remove the following line, or various
# that require network functionality will fail.
127.0.0.1 localhost
63.227.143.137 mail mail.csha.us

\etc\resolv.conf is.......
host = local, bind
nameserver 209.238.9.50
nameserver 209.238.9.51
nameserver 204.147.80.5

nslookup for our domain.......
> csha.us
Server: 209.238.9.50
Address: 209.238.9.50#53

csha.us mail exchanger = 50 mail.csha.us.

nslookup for another domain.....
> yahoo.com
Server: 209.238.9.50
Address: 209.238.9.50#53

Non-authoritative answer:
*** Can't find yahoo.com: No answer

Trying to send an email out gets the error, "550 5.1.2 <jeffkunkle2001@yahoo.com>... Host unknown (Name server: yahoo.com: no data known)"

Trying to send an email in from outside gets the error, "Connected to 63.227.143.137 but sender was rejected. Remote host said: 553 5.1.8 <jeffkunkle2001@yahoo.com>... Domain of sender address jeffkunkle2001@yahoo.com does not exist"

JeffreyKunkle

It would appear from their website here that your ISP has changed their DNS servers

Your /etc/resolv.conf needs to look like this

/etc/resolv.conf
host = local, bind
nameserver 209.238.9.50
nameserver 209.238.9.51
nameserver 205.171.3.65
nameserver 205.171.2.65

Pete

You're awesome Pete.
Sure enough, Qwest changed the DNS Servers and we never got notification. Worked like a charm once I made the changes.
Thanks a bunch!!!!!!!!!!