Amazon SES - Domain Identity vs Email Identity

Hi all,

New to using Amazon SES and had a brief question i was hoping someone could answer for me. If we add in a domain identity, does that mean we can use SES to send emails from any email account within that domain but that the original email sender can also still send emails on behalf of the domain?

e.g. our company is called MyCompany - our domain is with IONOS who currently send our emails, if we add a domain identity into Amazon SES for MyCompany.com, does that mean we can continue to use IONOS to send emails for some accounts (e.g. JohnSmith@MyCompany.com) but use SES to send out emails from other accounts (e.g. Support@MyCompany.com, marketing@mycompany.com)?

I know you can add in a single address and verify it by clicking a link in an email that SES sends to that address (and also updating the SPF record to mention amazon) will allow you to send from one account via SES but i'm unsure as to what the implications of adding an entire domain into SES are. If anyone can shed any light on this, that'd be great.

Thanks for any help.