Email Authentication - Set domain by default

Hi Team,

Is it possible to set domain by default when someone tries to authenticate using their emailid?

Intention is let’s say if someone having an email id called myemail@mylongemaildomain.com and according to current capability he has to enter his full email address and password to authenticate, instead of that is it possible to enter only prefix part (myemail) and set domain part by default (mylongemaildomain.com) during authentication using any keycloak settings ?

Thanks,
Anish