If you're moving from Hosted Exchange at CDS to Microsoft Office 365, differences in retention functionality should be understood by users and support staff.
In Microsoft Office 365, the managed folders, used to categorize messages by retention period, are no longer created in new mailboxes. Mailboxes that have been migrated from the CDS Hosted Applications Platform will retain their managed folders, but they will no longer be subject to their 90- or 180-day retention periods. Once your mailbox has migrated, all managed folders will fall under the 540-day maximum retention period established in the DAS IT manual.
All user-created folders at the root of the mailbox will be subject to a 540-day retention period.
Retention folders will be set in accordance with the DAS IT manual within the limitations of the Microsoft Office 365 platform:
Microsoft Office 365 processes retention for a mailbox at least once every seven days, although this could occur more frequently as resources permit in the Exchange Online environment. The retention tasks handle both the tagging and purging of messages. It is possible that you will temporarily see expired messages (0-day expiration) before the tasks process a particular mailbox.
E3 mailboxes in Microsoft Office 365 are set at a default 100 GB maximum size. The associated cost of the mailbox does not change based on space used, and it is not possible to increase any mailbox above the 100 GB limit. Once a mailbox has reached 100 GB, it will be unable to send messages until it has permanently deleted enough content to drop below 100 GB in size.
Shared mailboxes, resource mailboxes, and equipment mailboxes are limited to 50 GB.
When retention tags are first applied to a mailbox, it will cause the local Outlook client to sync a large amount of data. This will cause the Outlook client to appear to lag or freeze for periods of time. This is normal, if unfortunate, behavior and will clear up within a day or two depending on how large the mailbox is. Users may use OWA in the interim.