Connecting to Office 365 Calendar via EWS

OnceHub communicates with your Office 365 Calendar using the Exchange Web Services (EWS) API, a well-established official Microsoft protocol. All credentials and data traffic are fully encrypted. Learn more about how your sign-in credentials are stored and protected by OnceHub

In this article, you'll learn how to connect to your Office 365 Calendar via EWS. 

NoteMicrosoft does not support Transport Layer Security (TLS) below TLS version 1.2. Learn more about how Exchange/Outlook Calendar uses TLS

Connecting to your Office 365 Calendar via EWS

  1. Sign in to your OnceHub Account.
  2. Open the left sidebar, click on Profile, and select Calendar connection

    NoteIf you're connected to any other calendar, you will need to disconnect first. Existing bookings that have not yet taken place will not be added to your Office 365 Calendar after you connect. 

  3. Click the Connect button next to Office 365 Calendar via EWS (Figure 1).
    Figure 1: Calendar connection
  4. The Connect to Office 365 Calendar via EWS pop-up will appear (Figure 2).
    Figure 2: Connect to Office 365 Calendar via EWS pop-up
  5. Enter your Office 365 email address and password, as you normally would to sign into your mailbox via Outlook or any other method. Click Connect.
  6. If the connection is successful, the pop-up closes and you should see confirmation that you're connected to your Office 365 Calendar (Figure 3).
    Figure 3: Connected to Office 365 Calendar
  • If you're using ScheduleOnce, you have the option to configure the ScheduleOnce advanced integration settings. You can also click the Continue setup button in the What's next? section to access more options in ScheduleOnce.

If your Office 365 account is set up with 2-step verification, you must create an app password first. You then use this special password to connect your OnceHub Account to your Office 365 Calendar.

You're all set! You can now configure your Office 365 Calendar via EWS connection


You can also connect your Office 365 Calendar to OnceHub using an encrypted OAuth 2.0 connection.

Connection issues requiring additional information

Even if your credentials are correct, the connection might not be successful due to various Office 365 configurations. In that case, you may need to provide additional information. Learn more about troubleshooting Office 365 Calendar via EWS connection issues

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