good mail treated as spam

I recently found a good (non-spam) message in my spam folder that was really problematic for me to have missed. Argh! I’m trying to figure out what caused it to be marked Spam, so it doesn’t happen again.

I use Apple Mail. The sender is in my Previous Recipients list. From the log:

Predicted: Spam (99)
…] matched rule <Body (any text part) Contains "src=“cid:”> in SpamSieve blocklist

I’m not sure what this rule means (i.e., what “cid” is). Should I remove the rule from the blocklist?

Thanks for any help.

“cid” has to do with an embedded image. It’s better to train the message as good than to remove the rule from the blocklist.