OneSignal - Customer engagement platform used by over 1 million developers and marketers; the fastest and most reliable way to send mobile and web push notifications, in-app messages, emails, and SMS.
MailStore - MailStore Home - A 100% free single-private-user desktop solution
Truepush - Unleash limitless possibilities with Truepush and save up to $600 monthly. Free up to 10K Subscribers on all features.
MailSteward - MailSteward : The Ultimate E-mail Manager for Mac OS X
PushCrew - Push Notifications for Websites
Gmvault - Backup the emails in your Gmail account.