Which email output does not require duplicative storage of attachments?

The correct answer is MHT, which stands for MIME HTML. This format allows for the encapsulation of a complete web page, including text, images, and attachments, within a single file. When emails are saved or exported in the MHT format, all relevant components are stored together, thus eliminating the need for duplicative storage of attachments.

In contrast, other formats or systems, like Gmail, Lotus Notes, and Outlook, typically manage email attachments separately from the message itself. For example, in Gmail, attachments are stored as separate files that are linked to the email, which could lead to redundancy if multiple emails share the same attachment. Similarly, Outlook and Lotus Notes also handle attachments in a way that may require them to be stored independently of the message, resulting in the possibility of duplicate copies depending on user actions or how the email is managed.

Using the MHT format streamlines storage by keeping everything integrated into a single file, which is particularly advantageous for preserving content integrity without redundancy.