Emails not being sent from Service Desk

Emails not being sent from Service Desk

Hey folks,

We noticed recently that the emails from the service desk have not been sending. Originally I thought it may have been a problem with our Email Security however after some investigation it looks like the emails are not being sent at all as they do not hit our email security at all.

I am looking for information on how to determine what the issue is. When you send emails manually you get the pop up that says "Approval Mail Sent" but I can't find any proof that they are actually sending and people are regularly not receiving them. 

Is there a way to see outgoing emails from the Service Desk? They send occasionally but its becoming more common that they are not sending. This goes for Approval notifications, request submission receipts and automated emails so it isn't just one component but the email overall.

Any advice is appreciated as this has been causing many issues for our workflows.

Thanks!