Update marketing permission by clicking URL from E-Mail

Hi Experts,

I have a requirement as below.

1. Through programming send an E-mail to the customer with URL.

2. Once customer opens the E-mail and clicks on URL, "E-Mail" Marketing permission should be set automatically in background for that customer.

To be more clear on requirement just take a example below.

when we register at SDN, we will receive a E-mail saying as thank you for registering with SAP ID Service.

To activate your account for SAP Community Network, click the link below.

when we click on the link Account will get activate.

Can anyone help me on this how to achieve this functionality.

Thanks & Regards

Raja