[[["わかりやすい","easyToUnderstand","thumb-up"],["問題の解決に役立った","solvedMyProblem","thumb-up"],["その他","otherUp","thumb-up"]],[["わかりにくい","hardToUnderstand","thumb-down"],["情報またはサンプルコードが不正確","incorrectInformationOrSampleCode","thumb-down"],["必要な情報 / サンプルがない","missingTheInformationSamplesINeed","thumb-down"],["翻訳に関する問題","translationIssue","thumb-down"],["その他","otherDown","thumb-down"]],["最終更新日 2025-09-04 UTC。"],[[["\u003cp\u003eThe Mail API allows sending emails with certain restrictions on allowed headers, including \u003ccode\u003eIn-Reply-To\u003c/code\u003e, \u003ccode\u003eList-Id\u003c/code\u003e, \u003ccode\u003eList-Unsubscribe\u003c/code\u003e, \u003ccode\u003eOn-Behalf-Of\u003c/code\u003e, \u003ccode\u003eReferences\u003c/code\u003e, \u003ccode\u003eResent-Date\u003c/code\u003e, \u003ccode\u003eResent-From\u003c/code\u003e, and \u003ccode\u003eResent-To\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eOutgoing emails can have file attachments, but certain filename extensions like \u003ccode\u003e.exe\u003c/code\u003e, \u003ccode\u003e.bat\u003c/code\u003e, and \u003ccode\u003e.vbs\u003c/code\u003e are prohibited for security reasons.\u003c/p\u003e\n"],["\u003cp\u003eThe MIME type of an attachment, which determines how the content is handled, is automatically inferred from the file extension, and if the extension is unknown, it will default to \u003ccode\u003eapplication/octet-stream\u003c/code\u003e.\u003c/p\u003e\n"],["\u003cp\u003eA wide range of MIME types and their corresponding file extensions are supported, covering various document, audio, image, and video formats.\u003c/p\u003e\n"],["\u003cp\u003eThis API is supported for first generation runtimes, and information on upgrading to second generation runtimes is provided.\u003c/p\u003e\n"]]],[],null,["# Mail with headers or attachments\n\nGo Java PHP Python\n\nWhen you send mail using the [Mail API](/appengine/docs/standard/services/mail),\nthere are some restrictions on the headers that you can use and the types of\nfiles you can attach.\n| This API is supported for first-generation runtimes and can be used when [upgrading to corresponding second-generation runtimes](/appengine/docs/standard/\n|\n| /services/access). If you are updating to the App Engine runtime, refer to the [Upgrade to second-generation runtimes]() page to learn about your migration options for legacy bundled services.\n\nOptional headers\n----------------\n\nAn outgoing email has headers that provide details about the message, such as\nthe sender, recipient, date, and subject. Each header has a name and a value.\nYou can also include the following headers in an outgoing email; for security\npurposes, other headers are not allowed:\n\n- In-Reply-To\n- List-Id\n- List-Unsubscribe\n- On-Behalf-Of\n- References\n- Resent-Date\n- Resent-From\n- Resent-To\n\nMail with attachments\n---------------------\n\nAn outgoing email message can have file attachments. Each attachment has a\nfilename and file data. The file data can come from any source, such as an\napplication data file or the datastore.\n\n### Filename extensions that are prohibited\n\nAs a security measure to protect against viruses, email attachments cannot use\nthe following filename extensions, and ZIP files cannot contain files with the\nfollowing filename extensions:\n\n- ade\n- adp\n- bat\n- chm\n- cmd\n- com\n- cpl\n- exe\n- hta\n- ins\n- isp\n- jse\n- lib\n- mde\n- msc\n- msp\n- mst\n- pif\n- scr\n- sct\n- shb\n- sys\n- vb\n- vbe\n- vbs\n- vxd\n- wsc\n- wsf\n- wsh\n\n### Attachments and Multipurpose Internet Mail Extensions (MIME) types\n\nThe MIME type of an attachment is determined from the file's extension. The MIME\ntype identifies the type of content that is being sent, and can determine how\nthat data is transferred.\n\nThe following is a list of MIME types and their corresponding filename\nextensions. You are not limited to these extensions, but if you use an unknown\nextension, App Engine will assign it the MIME type `application/octet-stream`."]]
