After enabling set mouse=a, text copied inside of Vim will not paste outside of Vim. Does anybody know of a way to fix this?
Here, selecting text with t
Add set clipboard=unnamed to your .vimrc. So it will use the clipboard register '*' instead of the unnamed register for all yank, delete, change and put operations (note it does not only affect the mouse).
The behavior of register '*' depends on your platform and how your vim has been compiled (or if you use neovim).
If it does not work, you can try with set clipboard=unnamedplus, but this option only makes sense on X11 systems (and gvim therefore).