MIME
MIME(Multipurpose Internet Mail Extensions)多用途互联网邮件扩展类型。是设定某种扩展名的文件用一种应用程序来打开的方式类型，当该扩展名文件被访问的时候，浏览器会自动使用指定应用程序来打开。多用于指定一些客户端自定义的文件名，以及一些媒体文件打开方式。
它是一个互联网标准，扩展了电子邮件标准，使其能够支持：
非ASCII字符文本；非文本格式附件（二进制、声音、图像等）；由多部分（multiple parts）组成的消息体；包含非ASCII字符的头信息（Header information）。
这 个标准被定义在RFC 2045、RFC 2046、RFC 2047、RFC 2048、RFC 2049等RFC中。 MIME改善了由RFC 822转变而来的RFC 2822，这些旧标准规定电子邮件标准并不允许在邮件消息中使用7位ASCII字符集以外的字符。正因如此，一些非英语字符消息和二进制文件，图像，声音 等非文字消息原本都不能在电子邮件中传输(MIME可以)。MIME规定了用于表示各种各样的数据类型的符号化方法。 此外，在万维网中使用的HTTP协议中也使用了MIME的框架，标准被扩展为互联网媒体类型。
中文名
多用途互联网邮件扩展
外文名
Multipurpose Internet Mail Extensions
外国语简称
MIME
应    用
客户端自定义的文件名

背景介绍

多用途互联网邮件扩展，它是一个互联网标准，在1992年最早应用于电子邮件系统，但后来也应用到浏览器。服务器会将它们发送的多媒体数据的类型告诉浏览器，而通知手段就是说明该多媒体数据的MIME类型，从而让浏览器知道接收到的信息哪些是MP3文件，哪些是Shockwave文件等等。服务器将MIME标志符放入传送的数据中来告诉浏览器使用哪种插件读取相关文件。
MIME能够支持非ASCII字符、二进制格式附件等多种格式的邮件消息。这个标准被定义在RFC 2045，RFC 2046，RFC 2047，RFC 2048，RFC 2049等RFC中。 由RFC 822转变而来的RFC 2822，规定电子邮件标准并不允许在邮件消息中使用7位ASCII字符集以外的字符。正因如此，一些非英语字符消息和二进制文件，图像，声音等非文字消息都不能在电子邮件中传输。MIME规定了用于表示各种各样的数据类型的符号化方法。
浏览器接收到文件后，会进入插件系统进行查找，查找出哪种插件可以识别读取接收到的文件。如果浏览器不清楚调用哪种插件系统，它可能会告诉用户缺少某插件，或者直接选择某现有插件来试图读取接收到的文件，或者可能会导致系统的崩溃。传输的信息中缺少MIME标识可能导致的情况很难估计，因为某些计算机系统可能不会出现什么故障，但某些计算机可能就会因此而崩溃。
检查一个服务器是否正确设置了MIME类型的步骤是：
  1. 在Netscape浏览器中打开服务器网页。
  2. 进入"Tools"菜单，选择"Page Info"。
  3. 在弹出的窗口中点击上层框架中的"EMBED"。
在下层框架中查看MIME的类型是否为"application/x-director"或"application/x-shockwave-flash"，如果是上述信息的话表明服务器已经正确设置了MIME类型；而如果MIME类型列出的是文本内容、八位一组的数据或是其它形式均表明服务器的MIME类型没有设置正确。
如果服务器没有正确标明其发送的数据的类型，服务器管理员应该正确添加相关信息，具体操作方法非常简单快捷。
Microsoft公司应用于Windows系统下的浏览器使用ActiveX控件，而不是Netscape插件，这种浏览器不必象其它浏览器那样依靠MIME的编码。"OBJECT"标签的"CLSID"属性准确地标明了应调用哪种程序来读取接收到的文件，因此浏览器不必象"EMBED"标签那样选择一种读取程序。正因为如此，你往往会在使用带插件的浏览器时遇到MIME问题，而使用ActiveX控件的浏览器则很少出现此类麻烦。
正由于上述工作方式的差别也解释了一种现象，不知你是否发现在使用Netscape浏览器播放WAV文件时，浏览器会调用LiveConnect插件进行播放，而其它浏览器一般都使用通用的QuickTime的播放插件等来进行播放，这是因为Netscape浏览器接收文件需要读取MIME标识符，以便决定调用哪种程序来读取接收的文件，而服务器设 置在Netscape浏览器中播放WAV文件应使用LiveConnect插件，因此Netscape浏览器接收到WAV格式的文件时必然就会调用 LiveConnect插件，但由于其它浏览器不使用这种方式，因此它们都使用系统默认的播放WAV格式文件的播放器。当然Flash电影文件并不存在这种问题，因为只有Flash播放器才能够正确读取这种格式的文件。
在把输出结果传送到浏览器上的时候，浏览器必须启动适当的应用程序来处理这个输出文档。这可以通过多种类型MIME（多功能网际邮件扩充协议）来完成。在HTTP中，MIME类型被定义在Content-Type header中。
例如，假设你要传送一个Microsoft Excel文件到客户端。那么这时的MIME类型就是“excel”。在大多数实际情况中，这个文件然后将传送给Excel来处理（假设我们设定Excel为处理特殊MIME类型的应用程序）。在ASP中，设定MIME类型的方法是通过Response对象的ContentType属性。

文件格式

最早的HTTP协议中，并没有附加的数据类型信息，所有传送的数据都被客户程序解释为超文本标记语言HTML 文档，而为了支持多媒体数据类型，HTTP协议中就使用了附加在文档之前的MIME数据类型信息来标识数据类型。
MIME意为多功能Internet邮件扩展，它设计的最初目的是为了在发送电子邮件时附加多媒体数据，让邮件客户程序能根据其类型进行处理。然而当它被HTTP协议支持之后，它的意义就更为显著了。它使得HTTP传输的不仅是普通的文本，而变得丰富多彩。
每个MIME类型由两部分组成，前面是数据的大类别，例如声音audio、图象image等，后面定义具体的种类。
常见的MIME类型(通用型)：
超文本标记语言文本 .html text/html
xml文档 .xml text/xml
XHTML文档 .xhtml application/xhtml+xml
普通文本 .txt text/plain
RTF文本 .rtf application/rtf
PDF文档 .pdf application/pdf
Microsoft Word文件 .word application/msword
PNG图像 .png image/png
GIF图形 .gif image/gif
JPEG图形 .jpeg,.jpg image/jpeg
au声音文件 .au audio/basic
MIDI音乐文件 mid,.midi audio/midi,audio/x-midi
RealAudio音乐文件 .ra, .ram audio/x-pn-realaudio
MPEG文件 .mpg,.mpeg video/mpeg
AVI文件 .avi video/x-msvideo
GZIP文件 .gz application/x-gzip
TAR文件 .tar application/x-tar
任意的二进制数据 application/octet-stream
用于WAP服务器的MIME类型有：
MRP文件（国内普遍的手机）
.mrp application/octet-stream
IPA文件(IPHONE)
.ipa application/iphone-package-archive

　　
.deb application/x-debian-package-archive
APK文件(安卓系统)
.apk application/vnd.android.package-archive
CAB文件(Windows Mobile)
.cab application/vnd.cab-com-archive
XAP文件(Windows Phone 7)
.xap application/x-silverlight-app
SIS文件(symbian平台/S60V1)
.sis application/vnd.symbian.install-archive *（下有）
SISX文件(symbian平台/S60V3/V5)
.sisx application/vnd.symbian.epoc/x-sisx-app
JAR、JAD文件(JAVA平台手机通用格式)
.jar .jad下面有
Internet中有一个专门组织IANA来确认标准的MIME类型，但Internet发展的太快，很多应用程序等不及IANA来确认他们使用的MIME类型为标准类型。因此他们使用在类别中以x-开头的方法标识这个类别还没有成为标准，例如：x-gzip，x-tar等。事实上这些类型运用的很广泛，已经成为了事实标准。只要客户机和服务器共同承认这个MIME类型，即使它是不标准的类型也没有关系，客户程序就能根据MIME类型，采用具体的处理手段来处理数据。而Web服务器和浏览器（包括操作系统）中，缺省都设置了标准的和常见的MIME类型，只有对于不常见的 MIME类型，才需要同时设置服务器和客户浏览器，以进行识别。
由于MIME类型与文档的后缀相关，因此服务器使用文档的后缀来区分不同文件的MIME类型，服务器中必须定义文档后缀和MIME类型之间的对应关系。而客户程序从服务器上接收数据的时候，它只是从服务器接受数据流，并不了解文档的名字，因此服务器必须使用附加信息来告诉客户程序数据的MIME类型。服务器在发送真正的数据之前，就要先发送标志数据的MIME类型的信息，这个信息使用Content-type关键字进行定义，例如对于HTML文档，服务器将首先发送以下两行MIME标识信息,这个标识并不是真正的数据文件的一部分。
Content-type: text/html
注意，第二行为一个空行，这是必须的，使用这个空行的目的是将MIME信息与真正的数据内容分隔开。
MIME利用了一个事实就是，RFC 822在消息体的内容中做了一点限制：唯一的限制就是只能使用简单的ASCII文本。所以，MIME信息由正常的Internet文本邮件组成，文本邮件 拥有一些特别的符合RFC 822的信息头和格式化过的信息体（用ASCII 的子集来表示的附件）。这些MIME头给出了一种在邮件中表示附件的特别的方法。

信息剖析

一个普通的文本邮件的信息包含一个头部分（To: From: Subject: 等等）和一个体部分（Hello Mr.,等等）。在一个符合MIME的信息中，也包含一个信息头并不奇怪，邮件的各个部分叫做MIME段，每段前也缀以一个特别的头。MIME邮件只是基 于RFC 822邮件的一个扩展，然而它有着自己的RFC规范集。
头字段
MIME头根据在邮件包中的位置，大体上分为MIME信息头和MIME段头。（译者：MIME信息头指整个邮件的头，而MIME段头只每个MIME段的头。）
MIME信息头有：
MIME-Version:
这个头提供了所用MIME的版本号。这个值习惯上为1.0。
Content-Type:
它定义了数据的类型，以便数据能被适当的处理。有效的类型 有：text，image，audio，video，applications，multipart和message。注意任何一个二进制附件都应该被叫 做application/octet- stream。这个头的一些用例为：image/jpg, application/mswork，multipart/mixed，这只是很少的一部分。
Content-Transfer-Encoding:
这是所有头中最重要的一个，因为它说明了对数据所执行的编码方式，客户/MUA 将用它对附件进行解码。对于每个附件，可以使用7bit，8bit，binary ，quoted-printable，base64和custom中的一种编码方式。7bit编码是用在US ASCII字符集上的常用的一种编码方式，也就是，保持它的原样。8bit和binary编码一般不用。对人类可读的标准文本，如果传输要经过对格式有影响的网关时 对其进行保护，可以使用quoted printable 。Base64是一种通用方法，在需要决定使用哪一种编码方法时，它提供了一个不用费脑子的选择；它通常用在二进制，非文本数据上。注意，任何非7bit 数据必须用一种模式编码，这样它就可以通过Internet邮件网关！
Content-ID:
如果Content-Type是message/external-body或multipart/alternative时，这个头就有用了，它超出了本文的范围。
Content-Description:
这是一个可选的头。它是任何信息段内容的自由文本描述。描述必须使用us-ascii码。
Content-Disposition:
一个试验性的头，它用于给客户程序/MUA提供提示，来决定是否在行内显示附件或作为单独的附件。
MIME段头（出现在实际的MIME附件部分的头），除了MIME- Version头，可以拥有以上任何头字段。如果一个MIME头是信息块的一部分，它将作用于整个信息体。例如，如果Content-Transfer- Encoding显示在信息（指整个信息）头中，它应用于整个信息体，但是如果它显示在一个MIME段里，它"只能"用于那个段中。
注意：其可以对自动对收到的邮件进行解密。

类型大全

格式前面为后辍名，后面为对应的MIME型（例如：rar application/x-rar-compressed 表示。RAR对应的是application/x-rar-compressed ）
{ ".323", "text/h323" },
{ ".3gp", "video/3gpp" },
{ ".aab", "application/x-authoware-bin" },
{ ".aam", "application/x-authoware-map" },
{ ".aas", "application/x-authoware-seg" },
{ ".acx", "application/internet-property-stream" },
{ ".ai", "application/postscript" },
{ ".aif", "audio/x-aiff" },
{ ".aifc", "audio/x-aiff" },
{ ".aiff", "audio/x-aiff" },
{ ".als", "audio/X-Alpha5" },
{ ".amc", "application/x-mpeg" },
{ ".ani", "application/octet-stream" },
{ ".apk", "application/vnd.android.package-archive" },
{ ".asc", "text/plain" },
{ ".asd", "application/astound" },
{ ".asf", "video/x-ms-asf" },
{ ".asn", "application/astound" },
{ ".asp", "application/x-asap" },
{ ".asr", "video/x-ms-asf" },
{ ".asx", "video/x-ms-asf" },
{ ".au", "audio/basic" },
{ ".avb", "application/octet-stream" },
{ ".avi", "video/x-msvideo" },
{ ".awb", "audio/amr-wb" },
{ ".axs", "application/olescript" },
{ ".bas", "text/plain" },
{ ".bcpio", "application/x-bcpio" },
{ ".bin ", "application/octet-stream" },
{ ".bld", "application/bld" },
{ ".bld2", "application/bld2" },
{ ".bmp", "image/bmp" },
{ ".bpk", "application/octet-stream" },
{ ".bz2", "application/x-bzip2" },
{ ".c", "text/plain" },
{ ".cal", "image/x-cals" },
{ ".cat", "application/vnd.ms-pkiseccat" },
{ ".ccn", "application/x-cnc" },
{ ".cco", "application/x-cocoa" },
{ ".cdf", "application/x-cdf" },
{ ".cer", "application/x-x509-ca-cert" },
{ ".cgi", "magnus-internal/cgi" },
{ ".chat", "application/x-chat" },
{ ".class", "application/octet-stream" },
{ ".clp", "application/x-msclip" },
{ ".cmx", "image/x-cmx" },
{ ".co", "application/x-cult3d-object" },
{ ".cod", "image/cis-cod" },
{ ".conf", "text/plain" },
{ ".cpio", "application/x-cpio" },
{ ".cpp", "text/plain" },
{ ".cpt", "application/mac-compactpro" },
{ ".crd", "application/x-mscardfile" },
{ ".crl", "application/pkix-crl" },
{ ".crt", "application/x-x509-ca-cert" },
{ ".csh", "application/x-csh" },
{ ".csm", "chemical/x-csml" },
{ ".csml", "chemical/x-csml" },
{ ".css", "text/css" },
{ ".cur", "application/octet-stream" },
{ ".dcm", "x-lml/x-evm" },
{ ".dcr", "application/x-director" },
{ ".dcx", "image/x-dcx" },
{ ".der", "application/x-x509-ca-cert" },
{ ".dhtml", "text/html" },
{ ".dir", "application/x-director" },
{ ".dll", "application/x-msdownload" },
{ ".dmg", "application/octet-stream" },
{ ".dms", "application/octet-stream" },
{ ".doc", "application/msword" },
{ ".docx", "application/vnd.openxmlformats-officedocument.wordprocessingml.document" },
{ ".dot", "application/msword" },
{ ".dvi", "application/x-dvi" },
{ ".dwf", "drawing/x-dwf" },
{ ".dwg", "application/x-autocad" },
{ ".dxf", "application/x-autocad" },
{ ".dxr", "application/x-director" },
{ ".ebk", "application/x-expandedbook" },
{ ".emb", "chemical/x-embl-dl-nucleotide" },
{ ".embl", "chemical/x-embl-dl-nucleotide" },
{ ".eps", "application/postscript" },
{ ".epub", "application/epub+zip" },
{ ".eri", "image/x-eri" },
{ ".es", "audio/echospeech" },
{ ".esl", "audio/echospeech" },
{ ".etc", "application/x-earthtime" },
{ ".etx", "text/x-setext" },
{ ".evm", "x-lml/x-evm" },
{ ".evy", "application/envoy" },
{ ".exe", "application/octet-stream" },
{ ".fh4", "image/x-freehand" },
{ ".fh5", "image/x-freehand" },
{ ".fhc", "image/x-freehand" },
{ ".fif", "application/fractals" },
{ ".flr", "x-world/x-vrml" },
{ ".flv", "flv-application/octet-stream" },
{ ".fm", "application/x-maker" },
{ ".fpx", "image/x-fpx" },
{ ".fvi", "video/isivideo" },
{ ".gau", "chemical/x-gaussian-input" },
{ ".gca", "application/x-gca-compressed" },
{ ".gdb", "x-lml/x-gdb" },
{ ".gif", "image/gif" },
{ ".gps", "application/x-gps" },
{ ".gtar", "application/x-gtar" },
{ ".gz", "application/x-gzip" },
{ ".h", "text/plain" },
{ ".hdf", "application/x-hdf" },
{ ".hdm", "text/x-hdml" },
{ ".hdml", "text/x-hdml" },
{ ".hlp", "application/winhlp" },
{ ".hqx", "application/mac-binhex40" },
{ ".hta", "application/hta" },
{ ".htc", "text/x-component" },
{ ".htm", "text/html" },
{ ".html", "text/html" },
{ ".hts", "text/html" },
{ ".htt", "text/webviewhtml" },
{ ".ice", "x-conference/x-cooltalk" },
{ ".ico", "image/x-icon" },
{ ".ief", "image/ief" },
{ ".ifm", "image/gif" },
{ ".ifs", "image/ifs" },
{ ".iii", "application/x-iphone" },
{ ".imy", "audio/melody" },
{ ".ins", "application/x-internet-signup" },
{ ".ips", "application/x-ipscript" },
{ ".ipx", "application/x-ipix" },
{ ".isp", "application/x-internet-signup" },
{ ".it", "audio/x-mod" },
{ ".itz", "audio/x-mod" },
{ ".ivr", "i-world/i-vrml" },
{ ".j2k", "image/j2k" },
{ ".jad", "text/vnd.sun.j2me.app-descriptor" },
{ ".jam", "application/x-jam" },
{ ".jar", "application/java-archive" },
{ ".java", "text/plain" },
{ ".jfif", "image/pipeg" },
{ ".jnlp", "application/x-java-jnlp-file" },
{ ".jpe", "image/jpeg" },
{ ".jpeg", "image/jpeg" },
{ ".jpg", "image/jpeg" },
{ ".jpz", "image/jpeg" },
{ ".js", "application/x-javascript" },
{ ".jwc", "application/jwc" },
{ ".kjx", "application/x-kjx" },
{ ".lak", "x-lml/x-lak" },
{ ".latex", "application/x-latex" },
{ ".lcc", "application/fastman" },
{ ".lcl", "application/x-digitalloca" },
{ ".lcr", "application/x-digitalloca" },
{ ".lgh", "application/lgh" },
{ ".lha", "application/octet-stream" },
{ ".lml", "x-lml/x-lml" },
{ ".lmlpack", "x-lml/x-lmlpack" },
{ ".log", "text/plain" },
{ ".lsf", "video/x-la-asf" },
{ ".lsx", "video/x-la-asf" },
{ ".lzh", "application/octet-stream" },
{ ".m13", "application/x-msmediaview" },
{ ".m14", "application/x-msmediaview" },
{ ".m15", "audio/x-mod" },
{ ".m3u", "audio/x-mpegurl" },
{ ".m3url", "audio/x-mpegurl" },
{ ".m4a", "audio/mp4a-latm" },
{ ".m4b", "audio/mp4a-latm" },
{ ".m4p", "audio/mp4a-latm" },
{ ".m4u", "video/vnd.mpegurl" },
{ ".m4v", "video/x-m4v" },
{ ".ma1", "audio/ma1" },
{ ".ma2", "audio/ma2" },
{ ".ma3", "audio/ma3" },
{ ".ma5", "audio/ma5" },
{ ".man", "application/x-troff-man" },
{ ".map", "magnus-internal/imagemap" },
{ ".mbd", "application/mbedlet" },
{ ".mct", "application/x-mascot" },
{ ".mdb", "application/x-msaccess" },
{ ".mdz", "audio/x-mod" },
{ ".me", "application/x-troff-me" },
{ ".mel", "text/x-vmel" },
{ ".mht", "message/rfc822" },
{ ".mhtml", "message/rfc822" },
{ ".mi", "application/x-mif" },
{ ".mid", "audio/mid" },
{ ".midi", "audio/midi" },
{ ".mif", "application/x-mif" },
{ ".mil", "image/x-cals" },
{ ".mio", "audio/x-mio" },
{ ".mmf", "application/x-skt-lbs" },
{ ".mng", "video/x-mng" },
{ ".mny", "application/x-msmoney" },
{ ".moc", "application/x-mocha" },
{ ".mocha", "application/x-mocha" },
{ ".mod", "audio/x-mod" },
{ ".mof", "application/x-yumekara" },
{ ".mol", "chemical/x-mdl-molfile" },
{ ".mop", "chemical/x-mopac-input" },
{ ".mov", "video/quicktime" },
{ ".movie", "video/x-sgi-movie" },
{ ".mp2", "video/mpeg" },
{ ".mp3", "audio/mpeg" },
{ ".mp4", "video/mp4" },
{ ".mpa", "video/mpeg" },
{ ".mpc", "application/vnd.mpohun.certificate" },
{ ".mpe", "video/mpeg" },
{ ".mpeg", "video/mpeg" },
{ ".mpg", "video/mpeg" },
{ ".mpg4", "video/mp4" },
{ ".mpga", "audio/mpeg" },
{ ".mpn", "application/vnd.mophun.application" },
{ ".mpp", "application/vnd.ms-project" },
{ ".mps", "application/x-mapserver" },
{ ".mpv2", "video/mpeg" },
{ ".mrl", "text/x-mrml" },
{ ".mrm", "application/x-mrm" },
{ ".ms", "application/x-troff-ms" },
{ ".msg", "application/vnd.ms-outlook" },
{ ".mts", "application/metastream" },
{ ".mtx", "application/metastream" },
{ ".mtz", "application/metastream" },
{ ".mvb", "application/x-msmediaview" },
{ ".mzv", "application/metastream" },
{ ".nar", "application/zip" },
{ ".nbmp", "image/nbmp" },
{ ".nc", "application/x-netcdf" },
{ ".ndb", "x-lml/x-ndb" },
{ ".ndwn", "application/ndwn" },
{ ".nif", "application/x-nif" },
{ ".nmz", "application/x-scream" },
{ ".nokia-op-logo", "image/vnd.nok-oplogo-color" },
{ ".npx", "application/x-netfpx" },
{ ".nsnd", "audio/nsnd" },
{ ".nva", "application/x-neva1" },
{ ".nws", "message/rfc822" },
{ ".oda", "application/oda" },
{ ".ogg", "audio/ogg" },
{ ".oom", "application/x-AtlasMate-Plugin" },
{ ".p10", "application/pkcs10" },
{ ".p12", "application/x-pkcs12" },
{ ".p7b", "application/x-pkcs7-certificates" },
{ ".p7c", "application/x-pkcs7-mime" },
{ ".p7m", "application/x-pkcs7-mime" },
{ ".p7r", "application/x-pkcs7-certreqresp" },
{ ".p7s", "application/x-pkcs7-signature" },
{ ".pac", "audio/x-pac" },
{ ".pae", "audio/x-epac" },
{ ".pan", "application/x-pan" },
{ ".pbm", "image/x-portable-bitmap" },
{ ".pcx", "image/x-pcx" },
{ ".pda", "image/x-pda" },
{ ".pdb", "chemical/x-pdb" },
{ ".pdf", "application/pdf" },
{ ".pfr", "application/font-tdpfr" },
{ ".pfx", "application/x-pkcs12" },
{ ".pgm", "image/x-portable-graymap" },
{ ".pict", "image/x-pict" },
{ ".pko", "application/ynd.ms-pkipko" },
{ ".pm", "application/x-perl" },
{ ".pma", "application/x-perfmon" },
{ ".pmc", "application/x-perfmon" },
{ ".pmd", "application/x-pmd" },
{ ".pml", "application/x-perfmon" },
{ ".pmr", "application/x-perfmon" },
{ ".pmw", "application/x-perfmon" },
{ ".png", "image/png" },
{ ".pnm", "image/x-portable-anymap" },
{ ".pnz", "image/png" },
{ ".pot,", "application/vnd.ms-powerpoint" },
{ ".ppm", "image/x-portable-pixmap" },
{ ".pps", "application/vnd.ms-powerpoint" },
{ ".ppt", "application/vnd.ms-powerpoint" },
{ ".pptx", "application/vnd.openxmlformats-officedocument.presentationml.presentation" },
{ ".pqf", "application/x-cprplayer" },
{ ".pqi", "application/cprplayer" },
{ ".prc", "application/x-prc" },
{ ".prf", "application/pics-rules" },
{ ".prop", "text/plain" },
{ ".proxy", "application/x-ns-proxy-autoconfig" },
{ ".ps", "application/postscript" },
{ ".ptlk", "application/listenup" },
{ ".pub", "application/x-mspublisher" },
{ ".pvx", "video/x-pv-pvx" },
{ ".qcp", "audio/vnd.qcelp" },
{ ".qt", "video/quicktime" },
{ ".qti", "image/x-quicktime" },
{ ".qtif", "image/x-quicktime" },
{ ".r3t", "text/vnd.rn-realtext3d" },
{ ".ra", "audio/x-pn-realaudio" },
{ ".ram", "audio/x-pn-realaudio" },
{ ".rar", "application/octet-stream" },
{ ".ras", "image/x-cmu-raster" },
{ ".rc", "text/plain" },
{ ".rdf", "application/rdf+xml" },
{ ".rf", "image/vnd.rn-realflash" },
{ ".rgb", "image/x-rgb" },
{ ".rlf", "application/x-richlink" },
{ ".rm", "audio/x-pn-realaudio" },
{ ".rmf", "audio/x-rmf" },
{ ".rmi", "audio/mid" },
{ ".rmm", "audio/x-pn-realaudio" },
{ ".rmvb", "audio/x-pn-realaudio" },
{ ".rnx", "application/vnd.rn-realplayer" },
{ ".roff", "application/x-troff" },
{ ".rp", "image/vnd.rn-realpix" },
{ ".rpm", "audio/x-pn-realaudio-plugin" },
{ ".rt", "text/vnd.rn-realtext" },
{ ".rte", "x-lml/x-gps" },
{ ".rtf", "application/rtf" },
{ ".rtg", "application/metastream" },
{ ".rtx", "text/richtext" },
{ ".rv", "video/vnd.rn-realvideo" },
{ ".rwc", "application/x-rogerwilco" },
{ ".s3m", "audio/x-mod" },
{ ".s3z", "audio/x-mod" },
{ ".sca", "application/x-supercard" },
{ ".scd", "application/x-msschedule" },
{ ".sct", "text/scriptlet" },
{ ".sdf", "application/e-score" },
{ ".sea", "application/x-stuffit" },
{ ".setpay", "application/set-payment-initiation" },
{ ".setreg", "application/set-registration-initiation" },
{ ".sgm", "text/x-sgml" },
{ ".sgml", "text/x-sgml" },
{ ".sh", "application/x-sh" },
{ ".shar", "application/x-shar" },
{ ".shtml", "magnus-internal/parsed-html" },
{ ".shw", "application/presentations" },
{ ".si6", "image/si6" },
{ ".si7", "image/vnd.stiwap.sis" },
{ ".si9", "image/vnd.lgtwap.sis" },
{ ".sis", "application/vnd.symbian.install" },
{ ".sit", "application/x-stuffit" },
{ ".skd", "application/x-Koan" },
{ ".skm", "application/x-Koan" },
{ ".skp", "application/x-Koan" },
{ ".skt", "application/x-Koan" },
{ ".slc", "application/x-salsa" },
{ ".smd", "audio/x-smd" },
{ ".smi", "application/smil" },
{ ".smil", "application/smil" },
{ ".smp", "application/studiom" },
{ ".smz", "audio/x-smd" },
{ ".snd", "audio/basic" },
{ ".spc", "application/x-pkcs7-certificates" },
{ ".spl", "application/futuresplash" },
{ ".spr", "application/x-sprite" },
{ ".sprite", "application/x-sprite" },
{ ".sdp", "application/sdp" },
{ ".spt", "application/x-spt" },
{ ".src", "application/x-wais-source" },
{ ".sst", "application/vnd.ms-pkicertstore" },
{ ".stk", "application/hyperstudio" },
{ ".stl", "application/vnd.ms-pkistl" },
{ ".stm", "text/html" },
{ ".svg", "image/svg+xml" },
{ ".sv4cpio", "application/x-sv4cpio" },
{ ".sv4crc", "application/x-sv4crc" },
{ ".svf", "image/vnd" },
{ ".svg", "image/svg+xml" },
{ ".svh", "image/svh" },
{ ".svr", "x-world/x-svr" },
{ ".swf", "application/x-shockwave-flash" },
{ ".swfl", "application/x-shockwave-flash" },
{ ".t", "application/x-troff" },
{ ".tad", "application/octet-stream" },
{ ".talk", "text/x-speech" },
{ ".tar", "application/x-tar" },
{ ".taz", "application/x-tar" },
{ ".tbp", "application/x-timbuktu" },
{ ".tbt", "application/x-timbuktu" },
{ ".tcl", "application/x-tcl" },
{ ".tex", "application/x-tex" },
{ ".texi", "application/x-texinfo" },
{ ".texinfo", "application/x-texinfo" },
{ ".tgz", "application/x-compressed" },
{ ".thm", "application/vnd.eri.thm" },
{ ".tif", "image/tiff" },
{ ".tiff", "image/tiff" },
{ ".tki", "application/x-tkined" },
{ ".tkined", "application/x-tkined" },
{ ".toc", "application/toc" },
{ ".toy", "image/toy" },
{ ".tr", "application/x-troff" },
{ ".trk", "x-lml/x-gps" },
{ ".trm", "application/x-msterminal" },
{ ".tsi", "audio/tsplayer" },
{ ".tsp", "application/dsptype" },
{ ".tsv", "text/tab-separated-values" },
{ ".ttf", "application/octet-stream" },
{ ".ttz", "application/t-time" },
{ ".txt", "text/plain" },
{ ".uls", "text/iuls" },
{ ".ult", "audio/x-mod" },
{ ".ustar", "application/x-ustar" },
{ ".uu", "application/x-uuencode" },
{ ".uue", "application/x-uuencode" },
{ ".vcd", "application/x-cdlink" },
{ ".vcf", "text/x-vcard" },
{ ".vdo", "video/vdo" },
{ ".vib", "audio/vib" },
{ ".viv", "video/vivo" },
{ ".vivo", "video/vivo" },
{ ".vmd", "application/vocaltec-media-desc" },
{ ".vmf", "application/vocaltec-media-file" },
{ ".vmi", "application/x-dreamcast-vms-info" },
{ ".vms", "application/x-dreamcast-vms" },
{ ".vox", "audio/voxware" },
{ ".vqe", "audio/x-twinvq-plugin" },
{ ".vqf", "audio/x-twinvq" },
{ ".vql", "audio/x-twinvq" },
{ ".vre", "x-world/x-vream" },
{ ".vrml", "x-world/x-vrml" },
{ ".vrt", "x-world/x-vrt" },
{ ".vrw", "x-world/x-vream" },
{ ".vts", "workbook/formulaone" },
{ ".wav", "audio/x-wav" },
{ ".wax", "audio/x-ms-wax" },
{ ".wbmp", "image/vnd.wap.wbmp" },
{ ".wcm", "application/vnd.ms-works" },
{ ".wdb", "application/vnd.ms-works" },
{ ".web", "application/vnd.xara" },
{ ".wi", "image/wavelet" },
{ ".wis", "application/x-InstallShield" },
{ ".wks", "application/vnd.ms-works" },
{ ".wm", "video/x-ms-wm" },
{ ".wma", "audio/x-ms-wma" },
{ ".wmd", "application/x-ms-wmd" },
{ ".wmf", "application/x-msmetafile" },
{ ".wml", "text/vnd.wap.wml" },
{ ".wmlc", "application/vnd.wap.wmlc" },
{ ".wmls", "text/vnd.wap.wmlscript" },
{ ".wmlsc", "application/vnd.wap.wmlscriptc" },
{ ".wmlscript", "text/vnd.wap.wmlscript" },
{ ".wmv", "audio/x-ms-wmv" },
{ ".wmx", "video/x-ms-wmx" },
{ ".wmz", "application/x-ms-wmz" },
{ ".wpng", "image/x-up-wpng" },
{ ".wps", "application/vnd.ms-works" },
{ ".wpt", "x-lml/x-gps" },
{ ".wri", "application/x-mswrite" },
{ ".wrl", "x-world/x-vrml" },
{ ".wrz", "x-world/x-vrml" },
{ ".ws", "text/vnd.wap.wmlscript" },
{ ".wsc", "application/vnd.wap.wmlscriptc" },
{ ".wv", "video/wavelet" },
{ ".wvx", "video/x-ms-wvx" },
{ ".wxl", "application/x-wxl" },
{ ".x-gzip", "application/x-gzip" },
{ ".xaf", "x-world/x-vrml" },
{ ".xar", "application/vnd.xara" },
{ ".xbm", "image/x-xbitmap" },
{ ".xdm", "application/x-xdma" },
{ ".xdma", "application/x-xdma" },
{ ".xdw", "application/vnd.fujixerox.docuworks" },
{ ".xht", "application/xhtml+xml" },
{ ".xhtm", "application/xhtml+xml" },
{ ".xhtml", "application/xhtml+xml" },
{ ".xla", "application/vnd.ms-excel" },
{ ".xlc", "application/vnd.ms-excel" },
{ ".xll", "application/x-excel" },
{ ".xlm", "application/vnd.ms-excel" },
{ ".xls", "application/vnd.ms-excel" },
{ ".xlsx", "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet" },
{ ".xlt", "application/vnd.ms-excel" },
{ ".xlw", "application/vnd.ms-excel" },
{ ".xm", "audio/x-mod" },
{".xml","text/plain"},
{".xml","application/xml"},[1] 
{ ".xmz", "audio/x-mod" },
{ ".xof", "x-world/x-vrml" },
{ ".xpi", "application/x-xpinstall" },
{ ".xpm", "image/x-xpixmap" },
{ ".xsit", "text/xml" },
{ ".xsl", "text/xml" },
{ ".xul", "text/xul" },
{ ".xwd", "image/x-xwindowdump" },
{ ".xyz", "chemical/x-pdb" },
{ ".yz1", "application/x-yz1" },
{ ".z", "application/x-compress" },[1] 
{ ".zac", "application/x-zaurus-zac" },
{ ".zip", "application/zip" },
{ ".json", "application/json" },

传输编码

内容传输编码（Content-Transfer-Encoding），这个区域使指定ASCII以外的字符编码方式成为可能。形式如下：
Content-Transfer-Encoding: [mechanism]
其中，mechanism的值可以指定为“7bit”，“8bit”，“binary”，“quoted-printable”，“base64”。
7bit
7bit这里指的是7位的ASCII编码方式。
8bit
8位元ASCII码。
binary
quoted-printable
因为欧洲的一些文字和ASCII字符集中的某些字符有部分相同。如果邮件消息使用的是这些语言的话，于ASCII重叠的那些字符可以原样使用，ASCII字符集中不存在的字符采用形如“=??”的方法编码。这里“??”需要用将字符编码后的16进制数字来指定。采用quoted-printable编码的消息，长度不会变得太长，而且大部分都是ASCII中的字符，即使不通过解码也大致可以读懂消息的内容。
base64
base64是一种将二进制的01序列转化成ASCII字符的编码方法。编码后的文本或者二进制消息，就可以运用SMTP等只支持ASCII字符的协议传送了。Base64一般被认为会平均增加33%的报文长度，而且，经过编码的消息对于人类来说是不可读的。
x-encodingname
这个值是预留的扩展。
参考资料