Mailspring - Mailspring is a mail client for Mac, Windows and Linux.

grepWin - grepWin is a simple search and replace tool which can use PCRE regular expressions to search for...

Thunderbird - Thunderbird is a free email application that's easy to set up and customize - and it's loaded with great features!

PowerGREP - Quickly search through large numbers of files on your PC or network using powerful text patterns to find exactly the information you want. Search and replace with plain text or regular expressions to maintain web sites, source code, reports, ...

The Bat - The Bat! is a secure desktop email client for Windows, designed to protect your correspondence against third-parties and to save your time.

dnGREP - dnGrep allows you to search across files with easy-to-read results.