Email images not loading in Outlook 2016

[Daniel Becroft]

Environment: JIRA 7.3.0#73011 (Server), LDAP authentication, no anonymous access

When viewing email notifications containing images in Outlook 2016 (desktop), the images do not load. Using some information gleaned from a previous issue back in 2012/2013[1], we have tried authenticating using Internet Explorer (and even Edge), to no avail. Note that everything works correctly in Outlook 2016 through the browser.

What we have noticed is:

1) Adding an image directly into the comment body does not work

2) Selecting an image from the dropdown of previously uploaded files works, but only for the thumbnail.

The thumbnail URL generated is /secure/thumbnail/xxxxx/_*.png, and the full image is generated as /secure/attachment/xxxxx/xxxxx_*.png

Possibly related, if I attempt to hit either of those URLs using cURL (or an equivalent), the file is returned with a Content-Type of text/plain, rather than image/png. This happens regardless of the Content-Type or Accept header values passed in the request.

Are there any other items that we can investigate?

[1] - https://community.atlassian.com/t5/JIRA-questions/How-to-get-images-in-Jira-s-HTML-emails-to-work-in-Outlook/qaq-p/145246)

[Andy Brook]

The 'text/plain' thing is  a bug in the JIRA rich text editor.  When used, in some situations, pasted images arent stored in JIRA as attachments with the correct mime type, this cascades allong to what you see, email clients may validate the content type declared and quite sensibly not try to render text/plain as an image.

https://jira.atlassian.com/browse/JRASERVER-64838 created 16 MAR

https://jira.atlassian.com/browse/JRASERVER-64320 created 7 MAR