It seems already “fixed” in the dev repository, but the latest released plugin (v2.0.5) zip does not include that file.
To fix it, downloaded the file directly from:
https://plugins.trac.ww.wp.xz.cn/browser/post-smtp/trunk/script/post-smtp-hooks.js
(look at the bottom for ‘Original Format’ for a download link).
I copied the file into: post-smtp/script/
sorry the formatting of the code block being converted by this website is not helping, but I guess you understand?
