error：Real domain name required for sender address。

原因是因为hostname不对，不能是localhost.localdomain。

修改：hostname -v lucifo。

/etc/hosts 中一定是127.0.0.1 localhost.localdomain

mc文件中一定要把 LOCAL_DOMAIN(`localhost.localdomain')dnl

改成LOCAL_DOMAIN(`lucifo')dnl

> jBH0CIxs030054: to=kd [at] netnerd.ca, ctladdr=root (0/0), delay=00:00:00,
> xdelay=00:00:00, mailer=relay, pri=57738, relay=[127.0.0.1]
> [127.0.0.1], dsn=4.0.0, stat=Deferred: Connection refused by
> [127.0.0.1]

Specify *both* IP interfaces in *.mc file you use to generate sendmail.cf
and recompile it.

DAEMON_OPTIONS(`Port=smtp,Addr=127.0.0.1, Name=MTA-local')dnl
DAEMON_OPTIONS(`Port=smtp,Addr=192.168.1.100, Name=MTA-public')dnl