Accountability - HMRC Email addresses allocation

As an accounting firm, we've been keeping track of which employees have used our email addresses since 2010. While we don’t store every individual email that has been sent, we do maintain a record of who was assigned to use our email accounts, whether they are still with us or have since left the company. This allows us to go back and identify which employee sent an email, ensuring accountability. With that in mind, From which year did HMRC begin recording the use of your hmrc.gov.uk email addresses, including those of both current and former employees? Is there any policy defines the accountability?

Hi,
Please can you forward your query to our Freedom of Information (FOI) team at:
foi.request@hmrc.gov.uk 
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Thank you.