When the External Storage Mode setting is set to IMAP, the Account Mailbox storage is extended using the external mailbox storage system, via IMAP connections:
- All external mailbox storage mailboxes are visible in the mailbox list. If there is a local Mailbox with the same name as an mailbox in external mailbox storage, the external mailbox is used.
- When a mailbox is being opened, a local Mailbox with the specified name is opened, if present. If not present, an IMAP connection to the external mailbox storage is created. It is used to open the specified external mailbox and to process mailbox operation by reading and modifying the external mailbox.
- When there is a request to create a mailbox, it is created locally, inside the CommuniGate Pro Account, if the requested Mailbox Class is not "Email" (empty), or if the parent mailbox is a Local Mailbox. In all other cases the mailbox is created in the external mailbox storage.