PO approval emails are reaching to approver after 2/3 hrs of submission

Summary:

Content (please ensure you mask any confidential information):

We are observing that, PO approval emails are reaching to approvers after 2/3 hrs of submission. This is not happening with any other approval emails.

1. PO is submitted for approval in Fusion
2. Pending approval notification is shown in Bell icon withing 5 seconds
3. Transaction Console also shows that the PO approval workflow is assigned to the approver within 2 secs of submission
4. But, The PO pending approval notification email is being received in Outlook 365 webmail/outlook app after 2/3 hrs of submission
5. All other approval pending emails are being received in outlook within 5 mins of submission