Z-Notifier

Z-notifier is a Firefox add-on that checks your webmail accounts and notifies the number of unread emails.

It's a fork of X-notifier 3.5.23, fixed to make it work on latest Firefox versions.

Requirements

Z-Notifier should work on Firefox 25 - 60, and possibly later versions.

But since Firefox 57, you may need to change some Firefox preferences in about:config:

extensions.legacy.enabled = true allows legacy extensions.
extensions.allow-non-mpc-extensions = true allows extensions not compatible with multi-process.
xpinstall.signatures.required = false allows unsigned add-ons (Mozilla no longer signs legacy extensions).
browser.tabs.remote.autostart = false disables multi-process.

See https://wiki.mozilla.org/Add-ons/Firefox57 for more information.

Note these preferences will have no effect for Firefox Beta and Release. Consider using Developer Edition or Nightly.

Download and Install

Available at release page: https://github.com/Loirooriol/Z-Notifier/releases

See Installation guide for details.

License

Z-notifier is based on X-notifier, so it's also licensed under GNU General Public License, version 2.0.

The software is provided "as is", without warranty of any kind. Legacy extensions are no longer supported by Firefox, and your Firefox profile could be damaged. Use at own risk.

Credit

Thanks a lot tobwithu, the creator of the original X-notifier extension.