安卓发送Exchange邮件，引用ews-android-api.jar和joda-time-2.8.jar两个包。
用法：
ExchangeService service = new ExchangeService(ExchangeVersion.Exchange2010_SP2);
ExchangeCredentials credentials = new WebCredentials("emailAddress", "password");
service.setCredentials(credentials);
service.setUrl(new URI("http://some-ews-server.com/EWS/Exchange.asmx"));
EmailMessage message = new EmailMessage(service);
message.getToRecipients().add("[email protected]");
message.setSubject("Hello world!");
message.setBody(MessageBody.getMessageBodyFromText("Sent using the EWS Android API."));
message.send();
