need help on my mail server

[John Paul Tomas [Yahoo!]]

im using fedore core 5. postfix / smtp.

Problems:

1. Cant seem to receive any mails, but i can send. 
2. nslookup / dig mx seems ok.
3. when sending emails the account need an entire
domain name like account at ns1.domain.com not the usual
account at domain.com
4. workstations cannot connect to the server using
their gui mailbox. 

Please advice.
Thanks


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