Roundcube - Web-based IMAP email client

PopTrayU - Have you fallen in love with the fabulous email notifier program Poptray, but you're running a...

Shift - Shift is the ultimate email client for managing Mail, Calendar, Drive, Slack, Asana, Jira, Evernote, and all your other favourite apps

Checker Plus for Gmail - Displays new emails and the sender's contact photo, get notifications or even listen, read or...

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

Gmail Notifier (restartless) - is a highly customizable browser extension that notifies you about the incoming emails from all your Google-Mail accounts and labels. Gmail notifier is available for Firefox, Chrome, Opera and Safari.