Over the course of our migration from Zimbra to Office 365, some issues have come to our attention.

• The Global Address List (GAL) appears incomplete: The Global Address List on Office 365 currently contains users which have been migrated to Office 365; it does not include users still using Zimbra or users on Google Apps for Education.
• Time zone issues: Your time zone is manually set from within Office 365. It is possible that your account, or the account of the user you are trying to interact with has their account set to a different time zone.
• Read receipts contain a timestamp from UTC: There is also a time zone issue due to Microsoft's Exchange servers being based on UTC time; HMC Office 365 cloud services use these servers for timestamps on read reciepts and meeting responses.
• When contacts were imported to Office 365, distribution lists and groups do not import:  Distribution Lists and Groups were features specific to Zimbra. New groups can be created in Outlook by following documentation here.
• Calendars opened and shared in the Outlook 2011 desktop app for Mac are unavailable in the web app (and vice versa): Due to limitations in connectivity between Microsoft's web app and desktop applications for OS X, shared calendars must be opened on both platforms to be visible on both platforms.
• Message/meeting tracking does not appear to be working: In order to use tracking of meeting responses in Office 365, you must be sending messages/meeting requests to addresses selected from the Global Address List (GAL), not to firstname_lastname@hmc.edu, Zimbra (@mailbox-01.hmc.edu) or Google Apps for Education (@g.hmc.edu) addresses.
• Send as multiple accounts: Depending on their job function, some users were able to send email as another address/user from within a single Zimbra account. This functionality can be recreated by working with CIS.
• Contacts on iOS devices appear multiple times: This is an issue specific to iOS devices (iPhone, iPad). When setting up an Office 365 account on iOS devices we recommend not syncing contacts.