Bob Alice wrote:

> \caption{5\% \label{_fred}}
> \autoref{alice} envolope
>
> When I spell-check this it fails to notice that 'envolope' is mis-spelled.
[...]
> I'm using emacs version 24.4.1 and aspell version 3.1.20 (but really
> 0.60.7-20110707); The default packages are from the Debian Jessie repo.

I see this on Debian testing with the same aspell and Emacs 24.5, but
not with 25.1. So I suggest you upgrade Emacs.