We are currently migrating from Exchange 2013 with Sophos Gateway to Exchange Online with Sophos Mailflow but unclear how to proceed. I've requested support a number of times but they keep pointing to a document that that outlines the move M365 Gateway to M365 Mailflow which isn't what I'm doing.
I really need a step by step guide on how to go about this an timing. I've completed a 90% data migration of all mailboxes so would the Sophos move take place now or after a complete migration, where would this leave the on-site server if moved now?
The first stage of the setup asks the question am I copying the M365 domain or setting up domain manually, I'm assuming manually as I assume exiting means I'm already using the gateway product for M365? Any pointer would be helpful.