sendmail not deliverig local mail without network

I just made a new installation of FreeBSD 10.2. Network is configured as DHCP, IPv4 only. When I have a working network connection when sendmail is started, then sendmail delivers local mail, even when I disconnect the network. If I start without network, then sendmail does not deliver local mail - and it won't start to, even if a network is available later.

Could anybody provide me with a hint how to get sendmail to deliver local mail always (i.e. regardless of the network status)?
Ok, found the solution: sendmail wants a working DNS, so adding the hostname to /etc/hosts for solves the problem.