The 'Notify me when there are Dropbox email matching problems' setting generates a pop-up message on your Workbooks desktop if you've sent an email to your Dropbox which uses an Object Reference that cannot be found on your database.  (Object References are unique identifiers for records in Workbooks. If you use these in either the subject or the body of the email that you send to your Dropbox, the email will be linked to that record on your database.)

However, if you send an email to your Dropbox that includes an email address for which there is no record in your Workbooks database, you will not be notified. The email will be within your database (and can be found within the Email Landing Page) but won't be linked to specific Person or Lead record. If you add a Person or Lead record later that uses that email address, the email will be linked to the new record.

If you'd like to add an enhancement suggestion to our Ideas page so that you and others can vote on it and influence what functionality is included in the product please feel free to do so.