A、Desktop mail programs. B、Internet providers. C、Mail servers. D、Social networks. D事实细节题。短文最后提到，电子邮件软件不能左右网络服务提供商，而网络服务提供商也不能干涉电

It looks like a great time for e-mail but a lousy time for e-mail applications. These days, many home users never bother to download their e-mail, and the only threat Web mail sites face comes from other sites.(26)In its favor, Web mail offers a simpler setup: You need to know only a user name and a password, without any mysterious mail-server addresses. Once your account is active, you can use it from any Web-connected computer. Web-based mail systems also make it easy to keep a permanent address regardless of your Internet provider. Doing the same with desktop e-mail usually requires paying extra money for a domain name and spending extra time on mail settings.(28)By contrast, desktop mail programs let you read and compose mail without an Internet connection and don’t wrap advertisements around your mail. But their most important advantage is their separation of software and service. Because you can use more than one program with one mail service, you can choose an application with the features you like. And because you can also use one mail program with more than one mail service, desktop applications make your mail itself portable; you can back up your messages and take them with you after closing an account. If desktop mail software programmers had kept pace with Web mail developers, the two camps could have a fairly even fight. Unfortunately,(27)mail software developers can’t make Internet providers upgrade their mail services, and Internet providers can’t make mail-software developers modify their efforts. Unless that situation somehow changes, Web mail will continue to face few challenges outside of the social networks.
26. Which is a disadvantage of e-mail applications?
27. Which is most likely the biggest competitor of Web mail?
28. What can we learn from this passage?