Your Shift4Shop store is designed to send several emails to your shoppers for many different circumstances including:
New Order Confirmations
Order Status Changes
Waiting List Notifications
Newsletter Subscribing and Unsubscribing
The address these messages appear to be coming from can be set in either of two ways.
The global setting for the "from" address can be set by going to Settings > General > Store Settings and set it in the "Email" field. This setting will effectively make all emails sent by your store appear with this email address in the "From" field.
Individual Email Templates
You can also tailor individual emails to send from specific email addresses by editing the respective email's design template specifications. To do this, go to Settings > Design > Emails. Here you will be presented with every email template your store uses for various situations like the ones listed above. Click on the Edit button for the email you want to change, and place your desired "From" address in the template's "From Field.
The email will now send using the address you specified as the "From" address.