PUT /accounts/{accountId}/envelopes/{envelopeId}/recipients?resend_envelope=true

{
    "signers": [
        {
            "name": "Jane Doe",
            "email": "janesemail@outlook.com",
            "recipientId": "3",
            "recipientIdGuid": "13e30b8d-3dd6-48e8-ad12-15237611a463",
            "requireIdLookup": "false",
            "userId": "2c9e06eb-f2c5-4bef-957a-5a3dbd6edd25",
            "routingOrder": "1",
            "status": "sent"
        },
        {
            "name": "John Doe",
            "email": "johnsemail@outlook.com",
            "recipientId": "1",
            "recipientIdGuid": "c2273f0f-1430-484a-886c-45ce2fb5e8a8",
            "requireIdLookup": "false",
            "userId": "03c8a856-c0ae-41bf-943d-ac6e92db66a8",
            "routingOrder": "1",
            "note": "",
            "roleName": "Signer1",
            "status": "sent",
            "templateLocked": "false",
            "templateRequired": "false"
        }
    ],
    "agents": [],
    "editors": [],
    "intermediaries": [],
    "carbonCopies": [],
    "certifiedDeliveries": [],
    "inPersonSigners": [],
    "recipientCount": "2",
    "currentRoutingOrder": "1"
}

PUT https://{{env}}.docusign.net/restapi/{{version}}/accounts/{{acctId}}/envelopes/{{envelopeId}}/recipients?resend_envelope=true

{
  "signers": [
   {
      "recipientId": "3",
      "name": "Jane Doe",
      "email": "janesemail@outlook.com"
    }
  ]
}

?resend_envelope={true or false}

http://www.docusign.com/p/RESTAPIGuide/RESTAPIGuide.htm#REST API References/Modify or Correct and Resend Recipient Information.htm

You can use docusign's latest API using nuget package manager "DocuSign.eSign.Api".

    Since , I am using C#, so here is the code:
    //Very first prepare Recepients:

    Recipients recpnts = new Recipients
                {
                    //CurrentRoutingOrder = "1", // Optional.
                    Signers = new List<Signer>()
                {
                        new Signer
                        {
                            RecipientId = "1",
                            RoleName = "Prospect",
                            Email = "ert@gmail.com",
                            Name = "Shyam",
                        },
                    }
                };
// Call Envelopes API class which has UpdateRecepient Method

EnvelopesApi epi = new EnvelopesApi();

var envelopeId ="62501f05-4669-4452-ba14-c837a7696e04";

var accountId = GetAccountId();

// Get Status or Error Details.

var summary = recSummary.RecipientUpdateResults.ToList();

var errors = summary.Select(rs => rs.ErrorDetails).ToList();

// Method to get your Docusign Account Details and Authorize it.

private static string GetAccountId()
        {
            string username = "Account Email Address";
            string password = "Account Password;
            string integratorKey = "Your Account Integrator Key";

      // your account Integrator Key (found on Preferences -> API page)


            ApiClient apiClient = new ApiClient("https://demo.docusign.net/restapi");
            Configuration.Default.ApiClient = apiClient;

            // configure 'X-DocuSign-Authentication' header
            string authHeader = "{"Username":"" + username + "", "Password":"" + password + "", "IntegratorKey":"" + integratorKey + ""}";
            Configuration.Default.AddDefaultHeader("X-DocuSign-Authentication", authHeader);

            // we will retrieve this from the login API call
            string accountId = null;

            /////////////////////////////////////////////////////////////////
            // STEP 1: LOGIN API
            /////////////////////////////////////////////////////////////////

            // login call is available in the authentication api
            AuthenticationApi authApi = new AuthenticationApi();
            LoginInformation loginInfo = authApi.Login();

            accountId = loginInfo.LoginAccounts[0].AccountId;
            return accountId;
        }