RE: Migration of existing infrastructure (DC+exchange) to office 365

Hi ccnadmin7275,

Before answering your questions, I would like to confirm some information first:

1. For "I have 60 active users, plus a lot of additional mailboxes for guests or roles", what's the difference between these two types of mailboxes? Could you please provide more information about them?
For example, do the mailboes for guests or roles need to send/receive emails and own the credientials to sign in?

2. After the migration, do you want to reserve your local AD/Exchange(such as Hybrid) or just use the pure cloud side environment?

Any updates are appreciated.

Best regards,
Kid Yang