Create a shared mailbox in Outlook
See this article.
Step 1: Obtain the calendar sharing URL from Office 365
Open the calendar that you’d like to display on Synthesis.
Click the Settings Cog in the upper right corner, scroll to the bottom, and click View all Outlook Settings.
In the Calendar menu, click Shared calendars.
In the Publish a calendar section, select the calendar you’d like to share on Synthesis from the dropdown.
In the next dropdown, select the appropriate amount of detail to publish. “Can view all details” or “Can view title and locations” are common for calendars displayed on Synthesis.
Click Publish.
You’ll see two links appear, copy the HTML link to your clipboard.
Step 2: Add embed code to Synthesis
Click the pencil icon to open the Page Editor.
Click Insert and select Embed.
Paste the URL of the calendar into the URL field.
Click Insert.
