Split SMTP domain

Hello.  We currently use email symantec.cloud.  We have an internal Domino email system and we have a single SMTP domain.

We are looking to pilot Office365 email for a few users.  Could we configure Symantec.Cloud to send email for these pilot users to the Office365 SMTP servers whilst the remainder of email for the domain still comes to our onsite Domino SMTP servers?

Thanks.