I don't believe there is an actual listing of e-mail addresses. pluto77 taught me (and it has been very effective)
For email address contacts at hotel properties, Contact Marriott Rewards Customer Support at:
1 801 468 4000 (8:15am - 9:00pm, Monday - Friday, US Eastern time)
They are pretty good for all of the specifics, including GM's, Concierge's etc.
Reading through some of the threads over to the side in the More Like This column (in orange and blue off to the right) here's additional info for contacting a specific individual if you know their name (again from pluto);
With over 3600+ properties worldwide, I think maintaining email contacts on hotel webpages could get a bit daunting, with personnel changes (the emails seem to be assigned to individuals ie. email@example.com, not a group mailbox), where as phone numbers change far less often, if ever. That's just my speculation. There may be other reasons.
Hope that helps.