User Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:68.0) Gecko/20100101 Firefox/68.0

Steps to reproduce:

Thunderbird does not show the attachments on some emails (often sent from Apple iPhones). As an example, attached to this bug report you will find the source of an email which fails to display the attachment, even though it contains the following attachment header (and the accompanying base64 encoded data):

--Apple-Mail-448CDDE1-476C-43C8-838C-D5DE1DEF88C5
Content-Type: application/pdf;
name="Facturen 2de kwartaal 2019-Dane Meubelen.pdf";
x-apple-part-url=f_jxm8w9j20
Content-Disposition: attachment;
filename="Facturen 2de kwartaal 2019-Dane Meubelen.pdf"
Content-Transfer-Encoding: base64

Actual results:

There is no way to view or download the attachment

Expected results:

Thunderbird should show the attachment icon in the email list view, and Thunderbird should provide the usual way to open or save the attachment.

Yes, we know this problem. You need to view the e-mail as "original HTML" and then the attachment will show.

Apple turn over billions of dollars and that somehow entitles them to infringe international standards :-(