Who knew this was such a complex problem?
I never lived in a place with a community mailbox (at least, not when I was old enough to care about mail), so I had to ask other people about their experiences and checked the internet for ideas and general mailbox problems. A friend from Europe went on Google maps and showed me street views of previous residences that had community mailboxes.
Contexts for Community Mailboxes
Obviously apartment complexes and the like are candidates, but I was surprised to learn that cul-de-sacs or even regular streets can have community mailboxes. Houses scattered around a forest or farm homes tend to have community mailboxes on the main road, presumably for the benefit of the mailman.
Community Mailbox Advantages
1) much, much easier for mailmen
2) more secure, as they almost always require a key to access
3) less prone to vandalism (as it's a community area, plus it can't be knocked over as easily as a single mailbox standing free)
4) provides opportunity for strengthening community ties (people can great each other as they get their mail)
5) only actual mail can be delivered; non-mail can't be delivered to the mailbox itself (by friends, solicitors, what have you)... though this could possibly be a disadvantage as well
Community Mailbox Disadvantages
1) more prone to temperature extremes than attached-to-house mailboxes (no! my Christmas chocolate! T_T), though this applies to standing-free mailboxes as well
2) resident must leave home to pick up mail, which can be a problem for the elderly or those with limited mobility
3) mail access requires keys, which can be lost (or stolen!) (specifically, I'm concerned that the master key can be "lost" or copied and that a malicious party can take advantage)
4) somewhat redundant as packages must be delivered to home anyway
5) industrial-looking; community mailboxes are sterile and uncreative in shape (in my research, I found that standing-free mailboxes are often customized and can be very uniquely shaped)
The Bigger Question
All this made me question the scope of the assignment. Exactly how much are we allowed to change? The mailbox itself, or the existing mail delivery system as well? Are we being hypothetical, changing everything without regard to cost or feasibility of transition, or realistic, considering implementation in the existing mail delivery infrastructure? In addition, for whom exactly are we trying to make things easier: the delivery person, or the resident? Easiest of all for the delivery person would be if everyone just had a P.O Box, but that places too much stress on the resident, who would (probably) prefer everything delivered straight to their door.
As I was assigned to look at community mailboxes specifically, I decided to focus on creating a community mailbox system that while fitting into the current mail paradigm but also addresses a lot of the issues I discovered.
The Result
My first design is birdhouse-like, with many mailboxes attached to an inside wall. Wide surface areas of the individual boxes allows basic customization (like painting, modge podging, or whatever else). A separate box (perhaps underneath?) is for outgoing mail. I'm told wasps etc. love to live in structures like this, which is disconcerting, but perhaps discrete use of traps (not pictured) could prevent any insect problems.
The mailboxes themselves have a double-lid design and includes a loop for a lock. (Omit lock for convenience, provide lock for security.) The top lid provides additional weatherproofing.
The second design provides a slot (perhaps also protected by a lid?) in the back for mail delivery, and an optionally locked lid in the front for mail pickup.
Depending on the size of the structure, this could make it easier for the mailman to deliver (drop off on the side of the sidewalk or road) and for the resident to pickup (pick up on the side of the homes), as one or the other wouldn't have to walk around to the other side as they would on the first design.
These designs incorporate advantages numbers 1 through 4, and address disadvantages 1, 3, and 5. Anything more would require something other than a traditional community mailbox system.