Attachments has fileName undefined after parsing attachment with simpleParser (contentType: 'message/rfc822')

[Quesj]

I am trying to parse emails with a different set of attachments. One of the attachments are .msg/.eml files. Sometimes the simpleParser returns fileName: "undefined".

The MIME contents of the email before parsing are good. The only correlation I could find is that this (sometimes) happens when the attached email has contentType: 'message/rfc822'.

The file is not corrupted, only the fileName doesn't get properly parsed by simpleParser. As the company I am working for doesn't allow sharing sensitive information I can't provide the email it happens with. But I hope someone has the same issue or this might be a known bug?