There could be multiple email addresses that your customers write to, for contacting you. If you are subscribed to the current Freshdesk plans, you can set up multiple support email addresses starting from the Growth plan. However, if you are subscribed to a previous plan, you can start setting up multiple support email addresses from the Blossom plan onwards.
You could add only one support email address in the free Sprout plan to your Freshdesk account. In such cases, you can only edit the default email address and have a custom support email address added under Admin > Channels > Email.
Alternatively, you can upgrade to a higher plan after which you would be able to associate multiple email addresses with your Account.