Remove Components

You cannot remove those components, they are too deeply integrated. You can hide the "Chat" icon and Message menu by changing the Advanced option (see <Settings | General | Config Editor>) "mail.chat.enabled" to False, but this doesn't actually remove anything from the program. If there are similar ways to hide Calendar and Tasks, I don't know what they are.

I'm getting a little tired of software developers adding "extras" to the base application. I have at least three different applications with their own calendar that they insist is the best one out there. Hiding the apps, when that's possible, still contributes to bloatware. I'd rather they not be there in the first place. Rather than deeply integrate apps people may not want, why not use plugins like Firefox does? Let me decide which components I want to add.

I want a mail program, not a manage-my-entire-life program (my wife handles that).

As Lin wrote, Thunderbird does not have components. (except extensions which are optional). I personally don't use Thunderbird's calendar except for testing. And I am totally satisfied with the UI - I see one small calendar icon in the far left, and that's it. Custom install is, and always has been, for changing program location and setting some OS defaults.

bloatware is a euphemism for don't give me what the majority of other users want. If you are not using calendar and have no calendars connected, then that code is not in memory. So what's the problem except a philosophical preference?