attachment handling broken for Outlook 2007

The story so far: a customer upgraded from 3.12.2 to 3.13 and complained that Rich Text mail sent from Outlook 2007 resulted in attachments not being added to the issue. The customer says this used to work and understandably wants to know what changed.

Changes to the email handling between 3.12 and 3.13 result in attachments not being handled properly in some circumstances. The problematic email is multipart/related. The "attachment" has no Content-Disposition (which is normal for multipart/related) so we don't see it as an attachment. It also has no Content-ID so we don't see it as an inline. The result is it doesn't get attached to the JIRA issue.

Previously this worked because anything that wasn't text/plain would get attached.

From my reading of http://www.ietf.org/rfc/rfc2387.txt we need to attach everything in multipart/related except the "root" (the first part or the part specified by the start parameter) document. You don't need to specify Content-Disposition or Content-ID (the MUA is free to use some other Content-* field to relate the parts, presumably the Content-Location is being used here).

There is a JRA-10827 which claims that we treat multipart/related as a blob and just attach the whole thing as an eml but that clearly is no longer the case (and possibly hasn't been for a while).