Requests are logged whenever your application or server attempts to send an email to one of your customers via SendGrid. A delivery is recorded when a request to send an email results in the email being accepted by the receiving server. Note, however, this does not necessarily mean that the message reached the recipient’s inbox
Seeing requests and delivery next to one another and monitoring their trend over a period of time helps you identify and address amy bigger than usual gaps between the two. If you see the delivery number go below the normal levels, take a look at your email lists and clean them if necessary to remove invalid emails.