Report for capturing if incident created for first mailbox

Summary:

Dear All,

Hope you are doing well.

We have 2 mailboxes (Mailbox1 and Mailbox2) for which both Incoming and outgoing emails are enabled. Both the mailboxes are handled by different groups of Agents from different business units. 

If an email sent to Mailbox1, later it can eb assigned to Mailbox2. Now, we need to created a custom report to see how many incidents were created by sending email to Mailbox1. They might have assigned to Mailbox2 manually by agents but we need that stats for when Incidents were initially assigned to Mailbox1.

1. Email sent to Mailbox1 to created Incident.
2. Agent reviewed and found that is not the correct mailbox, he reassigned manually that incident to Mailbox2.