Additionally, Outlook for Windows and OWA have shown to be more reliable than Outlook for Mac. Assuming reliable coverage, you might, for example, be able to create new appointments on a device, but may not want to invite, accept, or decline meetings, or modify any recurring events, until you are using Outlook or OWA (or have successfully tested these functions on your device). Consider managing your appointments only from Outlook or OWA.Beware of dropped signals and poor coverage areas that could have an impact on your use of the calendar.Other suggestions for mobile device use:.If you are using an older device, such as a first generation iPhone or iPod Touch, you will not be able to rely on the calendar and should consider an upgrade.Update your phone/device software when prompted.For details, see the Microsoft article at. Mobile devices are known to have issues with ActiveSync, especially those running older versions of their system software.Make sure to use the most current version of your desktop client software, especially Office 2016 or 2019 (Windows), or 2016 or 2019 (Mac).However, to help work around these issues, the following is suggested: An exact cause is not always known and can vary from client to client. There are known issues that cause some email clients, especially older clients and those on some mobile devices, to provide inconsistent and unreliable updating of calendar information via Exchange ActiveSync.

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