Quick update: I tried settings the path myself in gnome schema to point to the bogofilter binary in my profile. After restarting evolution, I see now there is a words database in my home directory.

So, this may be the solution for me. However, it still leaves open the question of whether guix evolution pacakge should be providing paths for bogofilter or spamassassin at compile time, either by default or as an option. It seems that if you do nothing, by default users of evolution have no spam filtering, although it looks like they do.

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