It works on the moulinette (cli) and admin side.
Try adding more mail alias with yunohost user update USER --add-mailalias 'ALIAS@DOMAIN.COM',
then you’ll see your aliases with yunohost user info USER
I’ve package the application called “Email poubelle”, literraly “throwable email addresses” which allows you to make redirections to your real email address. For example, you could add an alias foo@yourdomain.org which points to admin@yourdomain.org or on another domain. And redirections can be easily removed.
The application is not official supported, so install it at your own risks. For now, the feedback it had say there are no problem installing and using it. But it is not compatible with the yunohost alias system.
To install, https://github.com/matlink/emailpoubelle_ynh
I am sorry but all the interface is in french. I’ll try to translate it when I’ll have some time available.