How do I send as a shared mailbox or Office 365 group?

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If you have access to a shared/delegate mailbox or Office 365 group, you can send emails as your shared mailbox or group.

Be sure you have been granted Send As permissions to your desired delegate/shared mailbox or Office 365 group

Navigate to email.msudenver.edu and sign in to your email.
Start to create a new email.
Click the three dots to the right of the Send and Discard buttons.
Click Show From.
Once From shows above To and Cc, click from.
Click Other email address... and type in the desired email address you want to send as.

Open the Outlook Desktop Application and make sure you are signed in.
Start creating a new email.
Click Options on the ribbon for the email window.
In the options tab click From in the Show Fields section.
Once the From tab shows above To and Cc, click From and click Other Email Address...
Type in your desired email address or click From... and search for your mailbox or group in the global address list and click OK.

Open the Outlook Desktop Application for Mac and make sure you are signed in.
Make sure that you have added your delegate mailbox you want to send as first. If not please refer to this link, How do I access a delegate Outlook mailbox?.
Start creating a new email.
Make sure the To and From Field are showing. If not, click the drop down arrow to show.
Click the drop down arrow closest to your name.
Click the desired mailbox you want to send as.

You are now able to send an email as your desired shared mailbox or Office 365 Group in the Outlook Web Application.

You are now able to send an email as your desired shared mailbox or Office 365 Group in Outlook Desktop App.

You are now able to send as your desired shared mailbox on the Outlook Desktop Application for Mac.