Content-Disposition Header Gets Ignored

If a custom Content-Disposition header is defined for an attachment, it will be ignored by an email client, because the same header has already been implicitly defined for the same attachment.

Pigging back on an example from the docs:

message = MessageSchema(
    subject='Fastapi-Mail module',
    recipients=recipients,
    html="<img src='cid:logo_image'>",
    subtype='html',
    attachments=[
            {
                "file": "/path/to/file.png",
                "headers": {
                    "Content-ID": "<logo_image@localhost>",

                    # This will be ignored.
                    "Content-Disposition": "inline; filename=\"file.png\""
                },
                "mime_type": "image",
                "mime_subtype": "png",
            }
        ],
)

This results in the following header for the attachment part:

--===============2467096897246519167==
Content-Type: image/png
MIME-Version: 1.0
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename*=UTF8''logo.png
Content-Disposition: inline; filename="logo.png"
Content-ID: <logo_image@localhost>

Consider checking if Content-Disposition header has been explicitly defined for an attachment, before implicitly adding it to its part. Relevant part of the code: https://github.com/sabuhish/fastapi-mail/blob/a95697251dd26804bc8ff3fe3e426a7f5723cf6a/fastapi_mail/msg.py#L66

This problem has been already mentioned in a closed issue, but perhaps was overlooked: https://github.com/sabuhish/fastapi-mail/issues/92#issuecomment-1017488844

sabuhish / fastapi-mail

Content-Disposition Header Gets Ignored #128