René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Sending SMIME messages with sendMail endpoint is broken.","articleBody":"### Describe the bug\n\nHello,\n\nWe are using Microsoft Graph Java SDK to send encrypted SMIME Messages.\nWe are already encrypting the content and provide a full MIME document to endpoint:\nhttps://graph.microsoft.com/v1.0/me/sendMail\n\nFor example our MIME Message looks like this (saved on content variable):\n\n```\nDate: Tue, 10 Feb 2026 11:24:45 +0000 (UTC)\nFrom: HenriettaM@xyz.onmicrosoft.com\nTo: xxx-test@gmx.de\nMessage-ID: \u003c....>\nSubject: Test2\nMIME-Version: 1.0\nContent-Type: application/pkcs7-mime; name=\"smime.p7m\"; smime-type=authEnveloped-data\nContent-Transfer-Encoding: base64\n\nMIAGCyqGSIb3DQEJEAEXoIAwgAIBADGCAdswggHXAgEAMIGPMHcxCzAJBgNVBAYTAkRFMQwwCgYD\n...\n\n```\n\nWe are using the following code snipplet to send the Email:\n\n```\ninitializeGraphClient();\nString encoded = Base64.getEncoder().encodeToString(content.getBytes());\n\nRequestInformation requestInfo = new RequestInformation();\nrequestInfo.httpMethod = HttpMethod.POST;\nrequestInfo.urlTemplate = \"{+baseurl}/users/{+email}/sendMail\";\nrequestInfo.pathParameters = new HashMap\u003c>();\nrequestInfo.pathParameters.put(\"baseurl\", \"https://graph.microsoft.com/v1.0\");\nrequestInfo.pathParameters.put(\"email\", config.getMailbox());\nrequestInfo.headers.put(\"Content-Type\", Set.of(\"text/plain\"));\nrequestInfo.setContentFromScalar(client.getRequestAdapter(), \"text/plain\", encoded);\n\nHashMap\u003cString, ParsableFactory\u003c ? extends Parsable>> errorMapping = new HashMap\u003c>();\nerrorMapping.put(\"4XX\", ODataError::createFromDiscriminatorValue);\nerrorMapping.put(\"5XX\", ODataError::createFromDiscriminatorValue);\n\nclient.getRequestAdapter().sendPrimitive(requestInfo, errorMapping, Void.class);\n```\n\nHowever our SMIME content is converted into an attachment and send as an attachment packed into a multipart/mixed structure by sending the Email.\n\nHere is what we get on the reciever side:\n\n```\nContent-Type: multipart/mixed;\n\tboundary=\"_002_155174533371770722695547_\"\nMIME-Version: 1.0\n\n--_002_155174533371770722695547_\nContent-Type: text/plain; charset=\"us-ascii\"\nContent-Transfer-Encoding: quoted-printable\n\n--_002_155174533371770722695547_\nContent-Type: application/pkcs7-mime; name=\"smime.p7m\"\nContent-Description: smime.p7m\nContent-Disposition: attachment; filename=\"smime.p7m\"; size=4483;\n\tcreation-date=\"Tue, 10 Feb 2026 11:33:38 GMT\";\n\tmodification-date=\"Tue, 10 Feb 2026 11:33:38 GMT\"\nContent-ID: \u003cC06558A1F17AA04CAE95309F8C325E89@namprd19.prod.outlook.com>\nContent-Transfer-Encoding: base64\n\nMIAGCyqGSIb3DQEJEAEXoIAwgAIBADGCAdswggHXAgEAMIGPMHcxCzAJBgNVBAYTAkRFMQwwCgYD\n```\n\nCan you fix sending a SMIME by using this sendMail endpoint or is there any alternative ways for sending SMIME with Graph API?\nWe basically followed the Example 4 in this documentation page:\n\nhttps://learn.microsoft.com/en-us/graph/api/user-sendmail?view=graph-rest-1.0&tabs=http#example-4-send-a-new-message-using-mime-format\n\n### Expected behavior\n\nSending SMIME messages should work with the sendMail endpoint when Content-Type is provided as text/plain.\n\n### How to reproduce\n\nSee the code snipplet above for example code.\nWe can also provide a full SMIME example content if you want.\n\n### SDK Version\n\n_No response_\n\n### Latest version known to work for scenario above?\n\n_No response_\n\n### Known Workarounds\n\n_No response_\n\n### Debug output\n\n_No response_\n\n### Configuration\n\n_No response_\n\n### Other information\n\n_No response_","author":{"url":"https://github.com/precoder","@type":"Person","name":"precoder"},"datePublished":"2026-02-10T14:04:42Z","url":"https://github.com/microsoftgraph/msgraph-sdk-java/issues/2544"}