English to Chinese Tech/Engineering IT (Information Technology) Webmail

In other cases, a company might make employees jump through so many security hoops to access their e-mail remotely that they use Webmail instead, says David Cowings, senior manager of operations in security response at Symantec. For example, employees might forward copies of inbound corporate e-mail to their Webmail account rather than go through a complicated process such as using a {rotating access key} to dial in through a VPN from home or while traveling.
轮转的访问密钥？这是什么样的东西？