you could attach any type of files in e-mail.
Ps reference to RFC2045~RFC2049 protocol.
RFC822 describe the basic protocol of e-mail.But its limitation is:
1.only recognize 7-bits ascii character
2.could not transfer multipart data ,as:image,audio.
So the point is to realize the idea of MIME.Then we could use MIME to format data and encode data and tranfer data.
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