java改造错误400错误请求

Question

我遇到了一个有趣的错误。我正在使用mailgun和改装软件通过我的应用程序发送电子邮件。在打开应用程序后的第一次尝试中，发送尝试总是返回一个改装错误（400个错误请求）。但是，所有后续尝试都会正确发送

MailGunClient接口：

公共接口MailGunClient{

@FormUrlEncoded
@POST("/messages")
void sendMessagePurchase(
        @Field("from") String from,
        @Field("to") String to,
        @Field("h:Reply-To") String replyToAddress,
        @Field("subject") String subject,
        @Field("text") StringBuilder text,
        Callback<Response> responseCallback);
}

方法实例化接口并尝试发送（MainActivity）：

 public void sendResume(String productID) {
    if (productID.equals(EMAILSKU)) {
        mMailGunClient = new RestAdapter.Builder()
                .setEndpoint("https://api.mailgun.net/v3/mg.resumetemplatepro.com")
                .setLogLevel(RestAdapter.LogLevel.FULL)
                .setRequestInterceptor(new RequestInterceptor() {
                    @Override
                    public void intercept(RequestFacade request) {
                        final String credentials = "api" + ":" + "key-c5b8f0c0c7dcaabc23075b977a7b7e43";
                        final String authString = "Basic " + Base64.encodeToString(credentials.getBytes(), Base64.DEFAULT);
                        request.addHeader("Authorization", authString);
                    }
                })
                .build().create(MailGunClient.class);

        StringBuilder messageBody = new StringBuilder();
        messageBody.append("Hello," + "\r\n" + "\r\n");
        messageBody.append("Thank you for purchasing a resume. You can view the resume at the following link: " + getResumeTemplateDownloadLink(pager.getCurrentItem()) + "\r\n" + "\r\n");
        messageBody.append("Regards," + "\r\n");
        messageBody.append("The Resume Template Pro Team");


        mMailGunClient.sendMessagePurchase("resume@mg.resumetemplatepro.com", customerEmailAddress, RBPEMAIL, "Resume Template Email",
                messageBody, new Callback<Response>() {
                    @Override
                    public void success(Response response, Response response2) {
                        System.out.println("Success");
                        Toast.makeText(getApplication(), R.string.successfully_sent, Toast.LENGTH_SHORT).show();
                        Apptentive.engage(MainActivity.this, "Post_Sale");
                    }

                    @Override
                    public void failure(RetrofitError error) {
                        Toast.makeText(getApplicationContext(), R.string.try_again, Toast.LENGTH_LONG).show();
                    }
                });


    } else if (productID.equals(RESUMECOVERLETTER)) {
        mMailGunClient = new RestAdapter.Builder()
                .setEndpoint("https://api.mailgun.net/v3/mg.resumetemplatepro.com")
                .setLogLevel(RestAdapter.LogLevel.FULL)
                .setRequestInterceptor(new RequestInterceptor() {
                    @Override
                    public void intercept(RequestFacade request) {
                        final String credentials = "api" + ":" + "key-c5b8f0c0c7dcaabc23075b977a7b7e43";
                        final String authString = "Basic " + Base64.encodeToString(credentials.getBytes(), Base64.DEFAULT);
                        request.addHeader("Authorization", authString);
                    }
                })
                .build().create(MailGunClient.class);

        StringBuilder messageBody = new StringBuilder();
        messageBody.append("Hello," + "\r\n" + "\r\n");
        messageBody.append("The user with e-mail " + customerEmailAddress + " has purchased a professional edit. They purchased " + getResumeTemplateDownloadLink(pager.getCurrentItem()) + "." + "\r\n" + "\r\n");
        messageBody.append("Regards," + "\r\n");
        messageBody.append("The Resume Template Pro Team");

        mMailGunClient.sendMessagePurchase("resume@mg.resumetemplatepro.com", RBPEMAIL, customerEmailAddress, "Resume Template Purchase",
                messageBody, new Callback<Response>() {
                    @Override
                    public void success(Response response, Response response2) {
                        System.out.println("Success");
                        Toast.makeText(getApplication(), R.string.edit_purchase, Toast.LENGTH_SHORT).show();
                        Apptentive.engage(MainActivity.this, "Post_Sale");

                    }

                    @Override
                    public void failure(RetrofitError error) {
                        Toast.makeText(getApplicationContext(), R.string.try_again, Toast.LENGTH_LONG).show();
                    }
                });


    } else {
        Toast.makeText(MainActivity.this, R.string.error, Toast.LENGTH_SHORT).show();
    }


}