How do I access a shared mailbox via Outlook Web?

If you have full access permission to a shared mailbox that appears in the address book, you can use Outlook Web App to open that mailbox.

1. Log into your Taylor mailbox in Office 365 (https://outlook.office365.com)
2. In the upper right corner of the screen, you should see a profile icon. Click it and select "Open another mailbox."  
    
3. In the search bar, type the specific email account and select Open. 
   
4. Your browser will open a new tab displaying the email account contents of this shared mailbox.

Ref: https://support.microsoft.com/en-us/office/open-and-use-a-shared-mailbox-in-outlook-web-app-bc127866-42be-4de7-92ae-1ef2f787fd5c