Getting wrong contentType from EML attachment

Question

I am using Microsoft Graph to fetch mail and I recently noticed when an email has a .eml attachment, there are two cases:

If the sender attach that email through drugging emails to the composer, the attachment will be an item attachment type. <-- I can handle this case
If the sender attaches a .eml file through clicking "attach file", that attachment will be a type of file attachment. Up to this point, I think it is fine to be a file attachment. But when I try to fetch that attachment, the attachment content type is application/octet-stream which is wrong. Shouldn't it be message/rfc822? With application/octet-stream, I cannot create that attachment from our server.

score 1 · Accepted Answer · edited Oct 07 '21 at 12:12

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It isn't wrong, application/octet-stream simply represents a generic/unknown binary file. From RFC 2046 § 4.5.1:

The "octet-stream" subtype is used to indicate that a body contains arbitrary binary data.

Your application can make its own determination on how to handle the file. In this case, the .eml is just a text file. You can simply fetch the attachment and treat it as raw text.

edited Oct 07 '21 at 12:12

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answered Mar 06 '19 at 15:16

Marc LaFleur

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Thanks for you reply Marc! But if there are other application/octet-stream attachments, how can I make that determination between eml and those other application/octet-stream attachments? – CipherText Mar 06 '19 at 19:40
The file extension should be `.eml` – Marc LaFleur Mar 07 '19 at 18:41
Make sense! Thanks! – CipherText Mar 08 '19 at 21:42

Getting wrong contentType from EML attachment

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