Short answer

You receive an email with the updated Client Master Report (CMR) for the following reasons:

You opened a new demat account with Arrow.

You recently modified your account details, such as a name change, address change, mobile number change, email change, updating income details or any other change in your demat account.

Your demat account was converted to a BSDA or a NON-BSDA.

As per the SEBI circular (PDF), you receive the updated CMR whenever your demat account is mapped or unmapped from a trading account.

You closed your Arrow account.

The validity of the updated CMR link is mentioned in the email you received.