Given a mail infrastructure on a shared hosting environment using ~10 main email inboxes and ~30 email inboxes for other purposes, all via IMAP.
We now want to migrate to Microsoft Exchange (using Exchange Online). We have to pay per inbox. This is possible to the 10 main email inboxes but too expensive for the 30 email inboxes for other purposes.
We cannot use aliases or shared inboxes because we have to write from those 30 email inboxes (set the correct sender).
I don't see any alternative here but here is my question:
Is it possible to combine protocols / email infrastructures? That means: Can I use Exchange Online only for some email adresses and another provider for all other email adresses?
This is not possible, because the MX record cannot be "split up", correct?