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THUNDERBIRD: the SUCCESS STORY of LINUX! - 6.4M in Donations
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From Wikipedia, the free encyclopedia
Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
Community icon by Alpár-Etele Méder, licensed under CC BY 3.0
If you've read the Radicale ticket you saw that the contributors agree with me and aren't eager to implement such a feature.
I'm just trying to help you. If you need email notifications you should look at groupware products like NextCloud, not CalDAV servers. But be aware that groupware software often implement some parts of their stack as proprietary or non-standard.