InfoClick from Nisus is without a doubt one of the best search tools for Apple's Mail app. Unlike the basic search feature in Mail, InfoClick uses a guided search process that not only allows you to narrow down search results quickly, but also helps you select the right phrases, keywords, and contact names to use to find that elusive email you need.
You can also use InfoClick to create notes that link directly to one or more emails.
If you've been struggling to find an email message that you know you received at one time or another, InfoClick may be the email search app you need.
InfoClick is $15.00. A 15-day demo is available.
See other software choices from Tom's Mac Software Picks.