If one of the companies whose stocks you hold announces a buyback, you may participate in the same if you wish to, through your broker (Zerodha).
If you are eligible for the buyback, you would receive a Tender form to your registered email id from the Company’s RTA. After filling in the details, you may send the form to firstname.lastname@example.org. Read more here.
Once the shares are tendered in the buyback, you would need to pass on the details of the shares tendered to email@example.com, so that the same is updated in your smallcase as well.