Email Software Resources

How best can you filter spam mails, I sometimes feel there are important mail that shouldn't be redirected to my spam box, so most times I clear my spam box without checking. Is there a way users can determine which spam is more important

Even though I do not use this tool at the moment, I am quite sure that it will improve my experience using Mail, however, I am not quite sure how they can be created nor how can they could be implemented.

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