A mail has enough points to be spam, but isn't marked as such!

Typically people who report this are seeing something like the following in the mail headers:

X-Spam-Status: No, hits=7.0 required=7.0

It is a little confusing, but there is no bug here. The confusion is caused by rounding. The message actually scored 6.950-6.999 (scores go to 3 decimal places), but the header only displays to a single decimal place. Therefore 6.9# (# is >= 5) rounds the whole value to 7.0.

If X-Spam-Level is enabled for rewriting, you can see that the integer value of the score is only 6 for this message:

X-Spam-Level: ******

since there are only 6 stars.

See also RoundingIssues