The "Accept Email" field in Luminate Online corresponds to the "Requests no Email" checkbox in Raiser's Edge (See pg 30 of the integration guide).

When someone opts-out of email in Luminate Online, that opt-out request will be sent to Raiser's Edge as a constituent update to that field. However, modifying that field in Raiser's Edge will not change it back in Luminate. The constituent would need to be opted back into email in Luminate Online. The change only syncs from Luminate Online to Raiser's Edge, not from Raiser's Edge to Luminate Online.