I'd like to know how can I identify which transport rule was applied to a specific email in Exchange Online?
You can check which rule was applied in Exchange Admin Center>Mail flow>Message trace.
Please see the following screenshot:
My 2nd question is related to the picture attached:
is the Guid mentioned belongs to one of the Exchange Transport rule or it's a miss leading and it's related to the impactful
Based on my test, this field should be in the format like <mail flow rule name>/<guid>.
Please see the screenshot:
While this guid (in my test 51d970e8-5fd5-4949-b863-e8301fd2f76a) does refer to the mail flow rule applied.
You can check a mail flow rule's guid either in Exchange Admin Center or via Exchange Online Powershell.
In Exchange admin Center:
In Exchange Online Powershell:
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