How a very long subject line gets MIME-Encoded by Web mailers

gistfile1.md

Original String:

Subject: 漢字、カタカナ、ひらがなとasciiの混じったとてもとてもとても長いSubjectを含んだヘッダーがどうencodeされるかのテスト

###gmail

Subject: =?ISO-2022-JP?B?GyRCNEE7eiEiJSslPyUrJUohIiRSJGkkLCRKJEgbKEJhc2NpaRskQiROOi4bKEI=?=
\t=?ISO-2022-JP?B?GyRCJDgkQyQ/JEgkRiRiJEgkRiRiJEgkRiRiRDkkJBsoQlN1YmplY3QbJEIkcjReJHMbKEI=?=
\t=?ISO-2022-JP?B?GyRCJEAlWCVDJUAhPCQsJEkkJhsoQmVuY29kZRskQiQ1JGwkayQrJE4lRiU5JUgbKEI=?=

mail.yahoo.co.jp

Subject: =?iso-2022-jp?B?GyRCNEE7eiEiJSslPyUrJUohIiRSJGkkLCRKJEgbKEJhc2NpaQ==?=
 =?iso-2022-jp?B?GyRCJE46LiQ4JEMkPyRIJEYkYiRIJEYkYiRIJEYkYkQ5JCQbKEJTdWJq?=
 =?iso-2022-jp?B?ZWN0GyRCJHI0XiRzJEAlWCVDJUAhPCQsJEkkJhsoQmVuY29kZQ==?=
 =?iso-2022-jp?B?GyRCJDUkbCRrJCskTiVGJTklSBsoQiA=?=

outlook.com

Subject: =?iso-2022-jp?B?GyRCNEE7eiEiJSslPyUrJUohIiRSJGkbKEI=?=
 =?iso-2022-jp?B?GyRCJCwkSiRIGyhCYXNjaWkbJEIkTjouGyhC?=
 =?iso-2022-jp?B?GyRCJDgkQyQ/JEgkRiRiJEgkRiRiJEgbKEI=?=
 =?iso-2022-jp?B?GyRCJEYkYkQ5JCQbKEJTdWJqZWM=?=
 =?iso-2022-jp?B?dBskQiRyNF4kcyRAJVglQyVAITwkLBsoQg==?=
 =?iso-2022-jp?B?GyRCJEkkJhsoQmVuY29kZRskQiQ1JGwbKEI=?=
 =?iso-2022-jp?B?GyRCJGskKyROJUYlOSVIGyhC?=

Mail.app

Subject: =?utf-8?B?5ryi5a2X44CB44Kr44K/44Kr44OK44CB44Gy44KJ44GM44Gq44Go?=
 =?utf-8?B?YXNjaWnjga7mt7fjgZjjgaPjgZ/jgajjgabjgoLjgajjgabjgoI=?=
 =?utf-8?B?44Go44Gm44KC6ZW344GEU3ViamVjdOOCkuWQq+OCk+OBoOODmA==?=
 =?utf-8?B?44OD44OA44O844GM44Gp44GGZW5jb2Rl44GV44KM44KL44GL44Gu?=
 =?utf-8?B?44OG44K544OIIA==?=

Original String with lots of space

漢字 カタカナ ひらがなと asci iの混じった とても とても とても長い Subject を含んだ ヘッダーが どう encode されるかの テスト

gmail

Subject: =?ISO-2022-JP?B?GyRCNEE7ehsoQiAbJEIlKyU/JSslShsoQiAbJEIkUiRpJCwkSiRIGyhCIGFzY2kgaRskQiROOi4kOBsoQg==?=
\t=?ISO-2022-JP?B?GyRCJEMkPxsoQiAbJEIkSCRGJGIbKEIgGyRCJEgkRiRiGyhCIBskQiRIJEYkYkQ5JCQbKEIgU3ViamVjdCAbJEIkcjReJHMbKEI=?=
\t=?ISO-2022-JP?B?GyRCJEAbKEIgGyRCJVglQyVAITwkLBsoQiAbJEIkSSQmGyhCIGVuY29kZSAbJEIkNSRsJGskKyROGyhCIBskQiVGJTklSBsoQg==?=````

outlook.com

Subject: =?iso-2022-jp?B?GyRCNEE7ehsoQiAbJEIlKyU/JSslShsoQiAbJEIkUiRpGyhC?=
 =?iso-2022-jp?B?GyRCJCwkSiRIGyhCIGFzY2kgaQ==?=
 =?iso-2022-jp?B?GyRCJE46LiQ4JEMkPxsoQiAbJEIkSCRGJGIbKEIg?=
 =?iso-2022-jp?B?GyRCJEgkRiRiGyhCIBskQiRIJEYkYkQ5JCQbKEIg?=
 =?iso-2022-jp?B?U3ViamVjdCAbJEIkcjReGyhC?=
 =?iso-2022-jp?B?GyRCJHMkQBsoQiAbJEIlWCVDJUAhPCQsGyhCIBskQiRJGyhC?=
 =?iso-2022-jp?B?GyRCJCYbKEIgZW5jb2RlIBskQiQ1GyhC?=
 =?iso-2022-jp?B?GyRCJGwkayQrJE4bKEIgGyRCJUYlOSVIGyhC?=

mail.yahoo.co.jp

Subject: =?iso-2022-jp?B?GyRCNEE7ehsoQiAbJEIlKyU/JSslShsoQiAbJEIkUiRpJCwkSiRIGyhC?=
 =?iso-2022-jp?B?IGFzY2kgaRskQiROOi4kOCRDJD8bKEIgGyRCJEgkRiRiGyhCIA==?=
 =?iso-2022-jp?B?GyRCJEgkRiRiGyhCIBskQiRIJEYkYkQ5JCQbKEIgU3ViamVjdCA=?=
 =?iso-2022-jp?B?GyRCJHI0XiRzJEAbKEIgGyRCJVglQyVAITwkLBsoQiAbJEIkSSQmGyhC?=
 =?iso-2022-jp?B?IGVuY29kZSAbJEIkNSRsJGskKyROGyhCIBskQiVGJTklSBsoQg==?=

Mail.app

Subject: =?utf-8?B?5ryi5a2XIOOCq+OCv+OCq+ODiiDjgbLjgonjgYzjgarjgaggYXNj?=
 =?utf-8?B?aSBp44Gu5re344GY44Gj44GfIOOBqOOBpuOCgiDjgajjgabjgoIg?=
 =?utf-8?B?44Go44Gm44KC6ZW344GEIFN1YmplY3Qg44KS5ZCr44KT44GgIA==?=
 =?utf-8?B?44OY44OD44OA44O844GMIOOBqeOBhiBlbmNvZGUg44GV44KM44KL?=
 =?utf-8?B?44GL44GuIOODhuOCueODiA==?=

Conclusion

Not a single MUA is RFC-compliant! I have to conclude it's RFC...

http://www.ietf.org/rfc/rfc2047.txt