I can not run the postmap when you try to run me says:

postmap:warnig: valid_hostname:misplaced delimiter .lan
postmap.fatal:unable to use my own hostname
postfix/postmap[872]:ftall unable to use my own hostnme

I am raising a mail server for a school project and got this error when configuring postfixadmin

I appreciate your help in advance
Do you have a value set for [font="Courier New"]myhostname[/font]? Is it the value that postmap claims it can't use? Does it resolve in DNS?

[You may run into trouble with other machines using such a name, but that may be a problem to handle later...]