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I sometimes recieve e-mails with empty CONTENT-ID.

Exemple:

Empty content-id, Content-Disposition: attachement

In most cases, the empty content-id belongs to an attachement, that is added to the email two times, once as correct inline attachement with a content ID, in the second, the content-disposition is : attachement instead and the content ID is empty.

Content-Disposition: inline

Is this a mail client bug ?

Joachim Sauer
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Hossam Oukli
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1 Answers1

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According to the MIME RFC a Content-ID is optional, but if present should be "world-unique" (which an empty string certainly isn't).

Personally I'd treat empty Content-ID to be identical to a missing Content-ID.

Community
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Joachim Sauer
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    And yes, it's probably a mail client bug that it's adding the attachment twice. Possibly they're trying to work around bugs in mail readers that don't handle inline parts correctly. – Bill Shannon Sep 04 '19 at 22:42