public class DecodeEmail {

    String API_KEY = 'YOUR_API_KEY_HERE';
    string endPointUrl = 'https://api.pdf.co/v1/email/decode';

    public void decodeEmail()
    {
        try
        {
            String jsonBody = '{ "url": "https://pdfco-test-files.s3.us-west-2.amazonaws.com/email-extractor/sample.eml", "inline": true, "async": false }';
            Http http = new Http();
            HttpRequest request = new HttpRequest();            
            request.setHeader('x-api-key', API_KEY);
            request.setEndpoint(endPointUrl);
            request.setHeader('Content-Type', 'application/json');
            request.setMethod('POST');            
            request.setBody(jsonBody);            
            HttpResponse response =  http.send(request);            
            Map<String, Object> json = (Map<String, Object>)JSON.deserializeUntyped(response.getBody());            
            if(response.getStatusCode() == 200) 
            {
                if ((Boolean)json.get('error') == false)
                {
                    System.debug('response.getBody() :: '+response.getBody());
                }
            }
            else
            {
                System.debug('Error Response ' + response.getBody());
                System.Debug(' Status ' + response.getStatus());
                System.Debug(' Status Code' + response.getStatusCode());
                System.Debug(' Response String' + response.toString());
            }
        }
        catch (Exception ex)
        {
            String errorBody = 'Message: ' + ex.getMessage() + ' -- Cause: ' + ex.getCause() + ' -- Stacktrace: ' + ex.getStackTraceString();
            System.Debug(errorBody);
        }
    }
}

@isTest
private class DecodeEmailTest {

    static testmethod void testDecodeEmail() {
        Test.startTest();
        Test.setMock(HttpCalloutMock.class, new DecodeEmailTest.DecodeEmailMock());
        DecodeEmail decodeEmail = new DecodeEmail();
        decodeEmail.decodeEmail();
        Test.stopTest();
    }

    public class DecodeEmailMock implements HttpCalloutMock {
        public HttpResponse respond(HTTPRequest req) {
            HttpResponse res = new HttpResponse();
            String testBody = '{"url":"https://pdf-temp-files.s3.us-west-2.amazonaws.com/ESRNUYPYS5RJIOJ8MT5DL8QLNOWMT3SG/email-extractor/sample.eml?X-Amz-Expires=3600\u0026X-Amz-Security-Token=FwoGZXIvYXdzEG0aDHKmifPGIYK8lSM0gyKCAUpezMRqX46NuUtPXmG01%2F36PDGpPjXHDmQF53pRl%2Bu9DjbpnNUp0iwxssel1HzjZNklih1l1C9BXEdEKn3Zea9N3mcADliD7g6Mxb8hr1rRz79U8GI6VlHIZZVJXbPRVyUyGrY%2BiwhfgarRg%2B5lln8jHMxPiHO66HUwGGkz04G4Iaoo0pOXoAYyKHe1LuYDaSM5gunLIezTYMm2wYrjgcOTQ%2F%2B07VwIFeBRaZFclBGBqk4%3D\u0026X-Amz-Algorithm=AWS4-HMAC-SHA256\u0026X-Amz-Credential=ASIA4NRRSZPHBI7XR2FE/20230306/us-west-2/s3/aws4_request\u0026X-Amz-Date=20230306T155547Z\u0026X-Amz-SignedHeaders=host\u0026X-Amz-Signature=e7d7005e0de47b9d065339883fd54f92f1eb18e14ae836c1c84eed56838fc29c","error":false,"status":200,"name":"sample.eml","credits":21,"duration":255,"remainingCredits":1165585}';
            res.setHeader('Content-Type', 'application/json');
            res.setBody(testBody);
            res.setStatusCode(200);
            return res;
        }
    }
}