Incoming postal mail
Postal mail is delivered by USPS to the mailbox attached to the exterior wall just to the left of the FrontDoor. Generally someone brings this in and places it in an appropriate mail slot in the MailMonolith, a giant wooden piece of furniture that probably used to be a wine rack. As a member, you will have a slot there with your name on it. (There may also be slots for former members, especially recent ones for whom a lot of mail still comes.) Feel free to decorate your mail slot, you don't have to settle for magic marker on masking tape!
Outgoing postal mail
Attach your properly addressed and stamped outgoing mail to the clip on the front of the mailbox outside the front door, and the nice postal worker will take it when they come by.
Generally, anyone here can, and will, sign for a package. Anything might happen after that, but a good rule of thumb if you sign for one is to place it on the floor by the mail monolith for the recipient to find. If you are expecting a package, you may wish to tell people to be looking out for it, possibly by posting a message on the HouseBusinessDiscussionList.
When you leave us, you might expect that you could get your mail forwarded in the usual manner. Unfortunately, because of our classification (as group housing?), the USPS *may* refuse to accept a change of address form having our address. We as an organization are responsible for forwarding mail. We don't currently have any formal rules or structures regarding this, so when you are preparing for a move it is wise to directly and individually notify everyone who might send you postal mail.
We have a "Return to Sender" stamp that we sometimes use, and when we use it the USPS delivery person does seem to take that mail away when we clip it to the mailbox. NOTE: If you try this, be sure to take a marker and black out the light grey barcodes that may appear anywhere on the envelope! otherwise, a postal machine may scan it and end up sending it right back to us.