Thanks for your reply.
I do not have domain name. I have 20-25 systems and a Linux server in a LAN. I want to implement mail server to use in LAN. I do not want to receive mails from outside LAN because I know I can't. I do not have domain name.
Postfix and Dovecot has been installed on Linux server. 20-25 Linux users has been created on the server. I want to send and receive mails between these 20-25 systems of LAN. Each system has thunderbird and we want to configure server's user's account on different systems.
What value should we give of 'myhostname' and 'mydomain' in main.cf of postfix?
Any other specific setting in main.cf which is necessary to send mails locally?
Do we need to change any value in dovecot.conf?
When I try to configure mail account in thunderbird, it is not able to find the mail account, but it finds if I configure same mail account in server's thunderbird (it is not allowed but I confirmed somehow.
Thanks again and Please help.