SymptomsI cannot send any emails from the server, not even via the command line.
[root@server01 ~]# telnet localhost 25
Connected to localhost.
Escape character is '^]'.
220 server01.domain.com ESMTP
451 qmail-spp failure: plugins/chkrcptto: child crashed (#4.3.0)
CauseThe device /dev/full is missing.
# ls -la /dev/full
ls: /dev/full: No such file or directory
ResolutionCreate the device to resolve the problem.
~# mknod -m 666 /dev/full c 1 7
~# chown root:root /dev/full