Strange attachments when receiving mails in Lotus Notes 8.5.2

When receiving emails from Confluence, 2 strange attachments are added to the mail, (see screenshot attached). This behaviour only occurs in Lotus Notes and Apple Mail and cannot be reproduced in Thunderbird or through a Webmail client.

Lotus Notes

The issue can occur when the "Keep in sender's format" option is selected in the Person document in the Domino Directory. Changing this to "Prefer MIME" resolves the issue. This can however lead to undesirable layouts from other email sources.

The issue may also occur because of preferences in the client. In the client, go to File -> Preferences -> User Preferences, and untick 'Show inline MIME images as attachments'. This can be done to all clients through a notes.ini variable pushed through a policy document.