mqueue(4) — File Formats
OSF
NAME
mqueue − Contains the log file and temporary files associated with the messages in the mail queue
SYNOPSIS
/usr/spool/mqueue
DESCRIPTION
The /usr/spool/mqueue directory contains temporary files associated with the messages in the mail queue and may contain the log file. Temporary files have names that include the mail queue ID (MQID) of the message for which the file was created:
dfMQIDData file
lfMQIDLock file
nfMQIDBackup file
qfMQIDQueue control file
tfMQIDTemporary control file
xfMQIDTranscript file for session
RELATED INFORMATION
Commands: sendmail(8)
Daemons: syslogd(8)