Meta Search - Search your Desktop, Google Drive, Dropbox, Gmail, Evernote.
Google Groups - Google Groups allows you to create and participate in online forums and email-based groups with a rich experience for community conversations.
Findo - Your smart search 🔍 assistant across personal cloud ☁️
Groups.io - Email and web based discussion group software, includes archiving, emails, wiki, polls, file...
FYI - Find your documents, like magic 🔮
Gaggle Mail - Gaggle Mail is a simple and easy to use email list manager.