Cutover Migration from Exchange 2007 to Office365 with Brightmail appliance

Good Morning,

for one of my client, I've to do a cutover migration from Exchange 2007 to Office 365.

My question regards message flow. At the moment mail messages are received by an appliance then routed to Exchange 2007. Can I maintain the appliance also when all mailboxes will be migrated to the cloud? With this approach I can avoid to modify MX record registration. I didn't found nothing about that on documentation.

Just to be more clear, I explainbetter with ascheme:

now: Internet --> local SMTP appliance --> HUB Exchange 2007 --> Mailbox

based on MS documention, after the migration (modifying MX record): Internet --> Cloud environment

My idea: Internet --> local SMTP appliance --> Cloud environment

Thanks

Bye