@RestResource(urlMapping='/IntershopRelatedAccounts/*')
//beginning of 1
global class IntershopInboundRestTofetchContacts {
@HttpGet
 global static void fetchRelatedAccountswithContacts(){
        String emailstr = RestContext.request.params.get('Email');


        // Search contacts
    List<Contact> cont = [ Select Id, Name, Email,AccountId,Current_Employee__c,Ecommerce_User__c,MailingCountry  from Contact where Email=:emailstr ];

    // When  contact does not exists
        if(cont.size()==0){
           List<String> sendTo = new List<String>();
           Email_Notify__c   emailaddress = Email_Notify__c.getValues('InboundEmailId');
     Messaging.SingleEmailMessage email = new Messaging.SingleEmailMessage();
             sendTo.add(emailaddress.EmailId__c);
         email.setSubject('Regarding creation of Accounts and Contacts ');
         email.setToAddresses(sendTo);
         email.setPlainTextBody('kindly create accounts and contacts');
    Messaging.SendEmailResult [] r = Messaging.sendEmail(new Messaging.SingleEmailMessage[] {email});

        }

@isTest
public class Test_IntershopInboundRest {
    public static testMethod void Test_1(){


        RestRequest req = new RestRequest();
        RestResponse res = new RestResponse();

    // pass the req and resp objects to the method
    req.requestURI = 'https://danaherlbs--test.cs86.my.salesforce.com/services/apexrest/IntershopRelatedAccounts?Email=vineet@gmail.com';
    req.httpMethod = 'GET';
    req.addHeader('Content-Type', 'application/json');
          RestContext.request = req;
          RestContext.response = res;
        string emailstr = req.params.get('Email');
       List<string> sendto = new List<string>();
        Account a= new Account();
        a.name='account';
        a.SAP_Account_Number__c='569';
        a.Inactive__c=false;
        insert a;
    contact c= new contact();
        c.LastName='vineet';
        c.AccountId=a.Id;
        c.MailingCountry ='India';
        c.Current_Employee__c=true;
        c.Ecommerce_User__c=false;
        c.Email='james@gmail.com';
           insert c;
     List<Contact> conlst=[select id ,Email from contact where Email=:emailstr];

    if(conlst.size()==0){
    Email_Notify__c emailnotify = new Email_Notify__c();
        emailnotify.Name='james';
        emailnotify.EmailId__c='james@gmail.com';
        insert emailnotify;
       Email_Notify__c emailcustset=[select Id, EmailId__c from Email_Notify__c where Id=:emailnotify.Id];
        system.debug('11111'+emailcustset.EmailId__c);

                    Test.startTest();


   IntershopInboundRestTofetchContacts.fetchRelatedAccountswithContacts();


        Test.stopTest();
    }

    }
}

The code is failing at this line
 'sendTo.add(emailaddress.EmailId__c);'
Error:- Attempt to de-reference the null object.