What is the MIME type of .eml files in emails

Question

I want to attach a MTA report (not delivered bounce mail) to an email, but what is the correct MIME type?

I fetch the full body of the MTA report with

$body = imap_fetchbody($this->Mailbox->stream, $this->header->uid, '', FT_UID);

But what is the correct MIME type for attached .eml files?

Have tried message/rfc822 but when you open the file in Thunderbird the popup windows is empty. Have also tried text/plain but then the attachment is opended as plain text. I want to open the attachment .eml as an email

When you receive a MTA report (not delivered) the bounce mail is always forwarded as an attachment

I want to attach the full MTA report + forwarded bounce mail to a new mail

Our (proprietary) mail client at work just sets `Content-Type: application/octet-stream; name="xxx.EML" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="xxx.EML"`, and is able to open the received attachment “as” an email again via double click, though I could not say whether that was not probably due to the registered file ending. What happens when you send yourself a mail in Thunderbird, that you just attached an EML file to - does it work as desired then? If so, check the source code of that mail. — CBroe, Jan 13 '21 at 09:20
@CBroe its seems to work with `application/octet-stream` create an answer :) — clarkk, Jan 14 '21 at 00:22

score 7 · Accepted Answer · answered Jan 14 '21 at 07:28

Content-Type: application/octet-stream should do the trick.

Our (proprietary) mail client at work just sets Content-Type: application/octet-stream; name="xxx.EML" Content-Transfer-Encoding: base64 Content-Disposition: attachment; filename="xxx.EML", and is able to open the received attachment “as” an email again via double click. Since that mime type is anything but specific, I suppose it falls back onto the file type handler registered for the .eml suffix on the OS level.

score 5 · Answer 2 · answered Apr 19 '22 at 17:12

5

message/rfc822 ("encapsulated message") works, at least with ReactDropzone. That string is what's reported as Type when an .eml file is dropped. (YMMV.)

answered Apr 19 '22 at 17:12

Freewalker

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That's also what the CLI tool `mimetype /path/to/file` tells me – Martin Thoma Oct 26 '22 at 07:45
I wish this is the selected answer. Email clients are just too flexible on this. `application/octet-stream` is for a generic file with bytes. – Kat Lim Ruiz Mar 05 '23 at 15:57

score 1 · Answer 3 · answered Jan 13 '21 at 09:36

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There is no mime type for it based on list as of 2020-12-23. See:

http://www.iana.org/assignments/media-types/media-types.xhtml

answered Jan 13 '21 at 09:36

Batyuvitez

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What is the MIME type of .eml files in emails

3 Answers3