Problem:
Qmail cant receive any email.

Error:
451 qmail-spp failure: plugins/chkrcptto: child crashed (#4.3.0) (in reply to RCPT TO command))

Cause:
Device /dev/full is missing.

#ls -al /dev/full
ls: /dev/full: No suce file or directory

How to fix:
mknod -m 666 /dev/full c 1 7
chown root:root /dev/full