What is the simplest way (or simplest library) to create a truly secure php mail() function?

The mail() function is bad, because it is so permissive with headers that yo开发者_StackOverflow中文版u pretty much can't use it with any user input without subjecting yourself or others to spam. So what is the simplest substitute that can still ensure that it's use is secure?

Ideally something that can be included in an external file.

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http://swiftmailer.org/ seems to be the most popular PHP OO solution currently