Time Delay between Email CreatedOn and QueueItem CreatedOn

Hi Friends,

We have a behavior here in which Contacts send email to Queues of our application.  There is a timelag or delay in the Email CreatedOn and QueueItem CreatedOn.  As QueueItem creation is out-of-box, we are finding it difficult to understand this behavior.

Of note, we have a Process which will be triggered on create of Email, which inturn will create a Case for this Email.  Also, we have one or two plugins registered on create and update message of Email and on update of QueueItem.  We have nearly 15000 Emails coming into the application everyday in our production environment.

Can anyone please let me know what might be causing this delay in creation of Email and it's QueueItem?

Thanks in advance for any hint or pointers.

--Palani