Change the address of the sending server

When we send a message we have this address : 2021-12-06-61ae43aaa2a3d4.24893413@idpartner.web56.lws-hosting.com with the name of the hosting.
We need our address : 2021-12-06-61ae43aaa2a3d4.24893413@idpartner.ourwebsite.com

Please someone can tell us where we can change this address ?

Thanks a lot

Best regards