In Evolution 3.34.1-2 (Ubuntu 19.10), I have selected a message, but the archive button – and the corresponding menu entry – is disabled. Why is that so?
And ‘yes’ – I have selected a folder to be the archives folder. You can spot it in the upper-left corner of the screenshot.
32 Answers
The "Archive" right-click menu requires you to first setup a dedicated folder. To that aim, create an "Archives" folder (any name will do), and then, in your account settings, set that folder to be the "Archive folder" (see Figure). This feature is also available in Thunderbird, and is set up in a similar way (under "Copies & Folders" in the "Account Settings" dialog).
Figure: The "Account Editor" screen in Evolution (Source)
If you are trying to set this up with Gmail, set your Evolution Archive folder to be the All Mail folder to preserve the "Gmail way" of IMAP organization.