Based on the verbosity level clapf syslog()s about its operation.

Normally (verbosity=1) clapf logs a single line, eg.

Sep 11 16:16:35 thorium clapf[28688]: 4aaa5bc2e143b68ed701d8833be296: from=Sonia.Qian2w@gmail.com, to=user@yourdomain.com, result=SPAM/0.9991, size=7626, attachments=0, relay=, delay=0.25, delays=0.00/0.07/0.01/0.00/0.00/0.00/0.10/0.00/0.00/0.00/0.07, status=250 2.0.0 Ok: queued as A90BC1D04C

4aaa5bc2e143b68ed701d8833be296 clapf queue identifier
from=Sonia.Qian2w@gmail.com sender address
to=user@yourdomain.com recipient address
result=SPAM/0.9991 the result of the spam check, and the probability of the message
size=7626 message size in bytes
attachments=0 number of attached files
relay= next hop
delay=0.25 overall processing time in seconds
delays=0.00/0.07/0.01/0.00/0.00/0.00/0.10/0.00/0.00/0.00/0.07 how much time (in seconds) clapf spent in the various phases
status=250 2.0.0 Ok: queued as A90BC1D04C answer of the next hop

The delays=a/b/c/d/e/f/g/h/i/j/k field consists of the following parts

a: lmtp/smtp conversation needed to get the message from the MTA
b: message parsing
c: antivirus scanning
d: query user data
e: query policy settings
f: minefield query
g: statistical check
h: training
i: token update
j: history store
k: smtp conversation with the next hop

verbosity=1 is the recommended setting for normal operation. If you want to debug something set verbosity=5, then /etc/init.d/rc.clapf reload to get a deep insight what clapf does under the hood.

Detailed logging

If you set verbosity=5, then clapf emits lots of syslog entries about what it does.