Comment 1 for bug 1517446

> The proposed change is to modify that default configuration to:
>
> DEFAULT_PASS_MIME_TYPES = ['multipart/mixed', 'multipart/alternative', 'multipart/signed', 'text/plain', ]

I mean:

DEFAULT_PASS_MIME_TYPES = ['multipart/mixed', 'multipart/alternative', 'multipart/signed', 'text/plain' ]