Use external mail service with own domain


I want to use Tutanota mail with my own domain like they advertise :
I have concerns about how things will play, because the domain is already used by yunohost, which has it own mail server.

My setup :
I have a VPS with yunohost and 2 domains registered. I don’t think it matters, but the domain I want to migrate to tutanota is not the main domain, let’s call it domain2. And they are not domains neither.

I already use mail addresses on domain2.
I’m fairly confident new email will go to Tutanota but will there be some conflicts on the VPS as Yunohost send notification email ? Should I remove some configuration in ynh postfix ? and more ?