請問postfix的安裝問題 - BBS

我用指令 cd /usr/ports/mail/postfix
make install clean後

出現以下的錯誤訊息

===> postfix-2.4.6,1 depends on shared library: sasl2.2 - found
Added group "postfix".
Added group "maildrop".
Added user "postfix".
You need user "postfix" added to group "mail".
Would you like me to add it [y]? y
上面這段跟講義一樣

但是到下面這段就出錯了
Updating /usr/local/share/doc/postfix/VIRTUAL_README...
Updating /usr/local/share/doc/postfix/XCLIENT_README...
Updating /usr/local/share/doc/postfix/XFORWARD_README...
postfix: warning: valid_hostname: empty hostname
postfix: fatal: unable to use my own hostname
*** Error code 1

Stop in /usr/ports/mail/postfix.
*** Error code 1

Stop in /usr/ports/mail/postfix.
*** Error code 1

Stop in /usr/ports/mail/postfix.
剛剛去網路上沒有找到安裝時產生這種錯誤訊息的解決方法

有沒有人有遇過這種情形的

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