Linux Sendmail and Fetchmail

I have installed Redhat Linux 7.1 on my server and configure my server Hostname as Linux123. I have configure to use Sendmail and Fetchmail to retrieved my Email from internet using SMTP protocol. My ISP mail server is mail.dns2go.com and my domain is abc.dns2go.com.
When I used the command #fetchmail -v it failed to retrieved the mail. The reply is shown below:
[root@linux1 /]#fetchmail ?v
fetchmail:SMTP<220 mail.dns2go.com ESMTP Mdaemon 5.0.1;Sun, 10, Feb 2002 05:23:49 ?0500 fetchmail:SMTP>EHLO linux123
fetchmail:SMTP<250-mail.dns2go.com Hello linux123, pleased to meet you fetchmail:SMTP<250-ETRN fetchmail:SMTP<250-AUTH LOGIN CRAM-MD5 fetchmail:SMTP<250-8BITMIME fetchmail:ETRN>ETRN linux123
fetchmail:ETRN<458 Node does not store mail here
fetchmail:Unable to queue message for node linux1
fetchmail:ETRN>QUIT
But when I changed my server Hostname to abc.dns2go.com it is able to retrieved mail. When use the commandd fetchmail -v the reply is shown below,
[root@linux1 /]#fetchmail ?v
fetchmail:SMTP<220 mail.dns2go.com ESMTP Mdaemon 5.0.1;Sun, 10, Feb 2002 05:23:49 ?0500 fetchmail:SMTP>EHLO abc.dns2go.com
fetchmail:SMTP<250-mail.dns2go.com Hello abc.dns2go.com, pleased to meet you fetchmail:SMTP<250-ETRN fetchmail:SMTP<250-AUTH LOGIN CRAM-MD5 fetchmail:SMTP<250-8BITMIME fetchmail:SMTP<250 SIZE 307200 fetchmail:SMTP<250-ETRN abc.dns2go.com fetchmail:ETRN>251 No message waiting for node
fetchmail:QUIT
It seemed that when set the Hostname the same as my domain abc.dns2go.com, I am able to retrieved the mail from mail.dns2go.com. But when I set the Hostname to Linux123 I am not able to retrieve any mail. How can I configure the Sendmail or Fetchmail to retrieved mail for abc.dns2go.com domain while configure my Hostname as Linux123.