It allows the choice of a binding to be deferred until runtime.
允许将绑定选择延后到运行时。
The two main reasons why the Ubuntu programmers have deferred making Thunderbird the default e-mail choice are it's lack of a built-in calendar and no Microsoft Exchange support.
Ubuntu程序员们决定推迟把Thunderbird作为默认Email选择的两个主要原因是:内建日历的缺少和没有对Microsoft Exchange的支持。
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