Apparently Aspose.Email is not able to determine the correct format of a msg attachment when embedded inside an .eml message.
Attachment format: “Eml”. ===> Expected was :“msg”.
Attachment content MIME type: “message/rfc822”. ===> Expected was :“application/octet-stream”.
I’ve tested this behaviour against an older version we used to use (5.5.0).
Counterproof: if you try to call FileFormatUtil.DetectFileFormat straight on the attachment file (“case 2a.msg” detached from the email) then Aspose detects the correct format.
You can test this behaviour using the script I’ve attached (Program.cs) and the test files, all of them are included in code_and_testfiles.zip (30.1 KB).