Invite guest fonction by mail don't work to share a librairie

Hello,
I got an error when I want to share a folder with a user using the “invite guest” function " the error is “emailrecipient@mail.com Failed to send email, email service is not properly configured, please contact administrator.”
The error only appears for external accounts such as gmail, icloud… for those of my companies it works, so the notification of account creation by email too, except for sharing librairies… if you have any ideas…

Thank you,