Not accessible to you on a regular basis.
I tend to locate the ‘mail’ statement in whatever form in use and add a second statement on the next line that appends the same info to a file. Depending on the volume of activity you can either come up with a script that manages regular archives or just do it manually. With dreamhosts email irregularites it’s a good measure.
Be sure to save the file at /home/USERNAME/ Or any place outside the webserver file path.