I have a limit I can tolerate, one emoji every other sentence.
I don’t use them in emails myself, but react emojis to internal work messages are fairly commonplace. A 👍 next to a message is often just a good way to know someone has confirmed reading something rather than needing to write “okay” which is ambiguous (what are you saying okay to?) and takes up space.
But I use a different range of emojis with different people when I do use them, to taste. With colleagues it’s one of 😁😆😅😕😯❤️👍👆, with friends it’s probably one of 🤣🤩😍🤔💀🧐😭🤯🥴😔😏😗💨 or 👀.
Using them to create tone and context is very helpful.
An example of where it’s excessive to me is Martin Wimpress’ Ubuntu MATE blog, like I know what a paper cut is, the emojis don’t add anything and are more of a nuisance to read. I think Martin has toned it down in his more recent posts.