Hi - I notice this is a forum backed by discourse. However, in its current state there is no way for users to opt into "mailing list mode". I have used this feature on other discourse forums and it works wonderfully without having to login to the forum via browser.
Additionally, please consider enabling reply by e-mail [1].
Strange, seems the attachment got mangled in transmission. It was supposed to be a single image file composed of 2 screenshots. Exporting to .jpeg seems to have fixed it:
@9peppe - it's a workaround and can work until admins enable mailing list mode. Drawback is having to manually subscribe to each category. If any new categories get added, then have to rinse and repeat.