Impossible de se connecter à mon client rainloop

hello i have a problem i just installed nextcloud 13 on my test server and i activated rainloop the problem is that i went on the admin interface of rainloop put my domain “” imap: and smtp: but when I want to login as a simple user I have a message "unreachable server"
what is the mistake and if anyone has an idea of ​​how to beat that I am a taker
thank you.