Hi! I want to make sure that users know about a certain rule before posting in a certain category. Can I show a message to users before or after posting in this category and/or send an automated message via Dicobot or Email?

So you want those creating topics in that category to have some guidance? Have you seen What are Topic Templates?

Envoi d'un message lors de la publication

isaac (Isaac Janzen) Septembre 19, 2022, 4:39 2

You could display a banner for a given category

Sujet		Réponses	Vues
Show customisable message on private topics/categories? Support	5	1150	Septembre 16, 2021
Display banner topic only to logged in users? Support	3	1302	Avril 17, 2019
Post or Topic Visibility Support	6	521	Novembre 8, 2023
Showing two banners: one to anonymous users, and one for logged-in members Support	5	1326	Mai 4, 2019
"This topic is only visible to those who can see the {x} category" message UX	3	598	Juillet 16, 2020