Backdate Personal Email with Attachments

I need a personal email backdated to appear as if it arrived last month in my Gmail. The email should include document attachments.

Requirements:
- Email should be visible in Gmail with a last month timestamp.
- Should include document attachments.
- Use of any tools or methods to achieve this is acceptable.

Ideal Skills:
- Experience with email manipulation.
- Familiarity with Gmail interface.
- Ability to include attachments in backdated emails.