When emailing out from CRM, you will need to select a queue to send from to ensure the email is sent correctly (you may notice that if you don't select a queue, the email will sit as Pending and won't actually send).
To select a queue, hover your mouse over the From field, then click on the search button on the right-hand side, and select Look Up More Records.
In the search box, change the Look for field to Queue, then type the name of the queue into the search box. Select the queue you'd like to use, then click Add.
You should now see the queue you've selected in the From field of the email.