It is used by Fastmail (who was also developers of the standard)
I think it is not a great idea to say that it is not a good idea to not implement things that no one uses, because that is a certain way to not make more people use it.
There are some servers that support it such as Stalwart [0], though I don't know about any older servers and/or clients that support it well.
I think it is not a great idea to say that it is not a good idea to not implement things that no one uses, because that is a certain way to not make more people use it.
There are some servers that support it such as Stalwart [0], though I don't know about any older servers and/or clients that support it well.
[0]: https://github.com/stalwartlabs/jmap-server