Office 365 - Find out which calendar system another person is using (e.g., Office 365 or other)

The following document explains how an individual using Office 365 can find out whether an email address:

  1. is on Office 365
  2. is using another calendar system outside of Office 365 (e.g., Exchange Server, Google Calendar, GroupWise, etc.)

If the individual has multiple email addresses, keep in mind that it is possible that different email addresses may be on different calendaring systems. If you aren't sure which email address to schedule with, you may want to contact the person to ask.


Is the person I am trying to schedule with using Office 365 or another external system?

To find out which calendar system another person is using, you will need to follow the steps below:

  1. First, check whether the person is using Office 365

    The best way to verify whether a person is using Office 365 is to check their availability. If their availability appears greyed out, they are not using Office 365. You can check availability via Outlook on the web or desktop Outlook. Select your preferred client below for instructions:

    •  If you are using Outlook on the web
      1. Use Office 365's Scheduling Assistant feature in Outlook on the web to check the availability of an event attendee.
      2. While checking availability, a user who's availability returns as a checkered grey box (as exampled below) is a part of an external calendaring system (non-Office 365) such as Google Calendar.

        check availability

    •  If you are using Outlook 2016/2013 for Windows
      1. Use the Outlook 2016 for Windows | Outlook 2013 for Windows Scheduling Assistant feature to check the availability of an event attendee.
      2. While checking availability, a user who's availability returns as a checkered grey box (as exampled below) is a part of an external calendaring system (non-Office 365) such as Google Calendar.

        check availability

    •  If you are using Outlook 2016 For Mac/Outlook for Mac 2011
      1. Open up Outlook and navigate to your calendar.
      2. Create a new event put the person's address in the attendees field.
      3. To verify if the person is in Office 365, we'll check their availability by clicking the Scheduling button.

        scheduling button

      4. While checking availability, a user who's availability returns as a checkered grey box (as exampled below) is a part of an external calendaring system (non-Office 365) such as Google Calendar.

        scheduling assistant

    •  If you are using Outlook 2010
      1. Open Outlook and navigate to your calendar.
      2. Create a new event and put that person's address in the attendees field.
      3. To check if the person is using Office 365, click the Scheduling Assistant button.
      4. While checking availability, a user who's availability returns as a checkered grey box (as exampled below) is a part of an external calendaring system (non-Office 365) such as Google Calendar.

        Outlook 2010 Office 365 check

  2. If the individual is not using Office 365, you only have two options

    • Before you send the calendar invitation, contact them and verify if they are available for the requested time.
    • Send the invitation and hope that they are available for the requested time.



Keywords:office 365 systems exists user calendar calendaring o365 how to find out which versus microsoft where scheduling assistant verify outlook web app 2016 2013 2010 2011 for mac windows   Doc ID:37626
Owner:Ara M.Group:Office 365
Created:2014-02-13 15:51 CDTUpdated:2016-06-22 11:46 CDT
Sites:DoIT Help Desk, DoIT Tech Store, Office 365, ShareURL, WiscCal
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