Result Based on a Single Token

I just noticed an email to a mailing list where it seems that a very
high spam probability was based on a single token that had only been
seen twice.

The filtering was done by Tuffmail, so I don't now any details about
the version, or configuration of Bogofilter.

Is this normal behaviour? It seems a bit reckless to me.



----------------------------------------------------------------------
Y 0.995766
   int  cnt   prob  spamicity histogram
  0.00    0 0.000000 0.000000 
  0.10    0 0.000000 0.000000 
  0.20    0 0.000000 0.000000 
  0.30    0 0.000000 0.000000 
  0.40    0 0.000000 0.000000 
  0.50    0 0.000000 0.000000 
  0.60    0 0.000000 0.000000 
  0.70    0 0.000000 0.000000 
  0.80    0 0.000000 0.000000 
  0.90    1 0.995766 0.995766 #

                                      n    pgood     pbad      fw     U
"changed"                            22  0.074890  0.014663  0.164021 -
"freebsd-questions"                 109  0.361233  0.079179  0.179839 -
"freebsd-questions-unsubscribe"     109  0.361233  0.079179  0.179839 -
"head:freebsd-questions"            109  0.361233  0.079179  0.179839 -
"head:freebsd-questions-request"     109  0.361233  0.079179  0.179839 -
"head:owner-freebsd-questions"      109  0.361233  0.079179  0.179839 -
"head:questions"                    109  0.361233  0.079179  0.179839 -
"rcvd:owner-freebsd-questions"      109  0.361233  0.079179  0.179839 -
"rtrn:owner-freebsd-questions"      109  0.361233  0.079179  0.179839 -
"head:Delivered-To"                 154  0.497797  0.120235  0.194582 -
"head:List-Post"                    154  0.497797  0.120235  0.194582 -
"head:FreeBSD.org"                   15  0.048458  0.011730  0.195277 -
"head:unsubscribe"                  160  0.515419  0.126100  0.196600 -
...
"rcvd:embarqmail.com"                 0  0.000000  0.000000  0.520000 -
"rcvd:mig01.embarq.synacor.com"       0  0.000000  0.000000  0.520000 -
"subj:Address"                        0  0.000000  0.000000  0.520000 -
"rcvd:questions"                     16  0.017621  0.035191  0.666178 -
"subj:Email"                          2  0.000000  0.005865  0.995766 +
N_P_Q_S_s_x_md                        1  0.004234  0.995766  0.995766
                                         0.017800  0.520000  0.375000

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