Getting RFC822 address parsing right took me a remarkably long time, not because any individual piece of it is hard but because it involved a pile of interdependent and fussy details.
The format of the file is similar to the manifest file -- a set of RFC-822 headers.
这个文件的格式类似于 manifest 文件 -- 一组 RFC-822 头。
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Many programs must accept E-mail addresses, but correctly handling all possible legal E-mail addresses (as specified in RFC 2822 and 822) is surprisingly difficult.