Exchange Group Mailflow

Hi

I have Groups in AD. These groups are MailEnabled Group and enabled on-prem and synced to the cloud

all the members are located in the cloud and using Exchange Online.

If one of these groups receives email from outside the organization, will the email go to on-premis and then the emails redirected from on-prem to the group, or Exchange have a cache of these groups and will send the email straight to the group members without having the email sent to on-premis

Thanks