A message to an MIT address which is returned to the sender with a message saying "beader hobo" is caused by a malformed Message-ID field in the header. The Message-ID field is a unique identifier for each message, which enables tracking of that message.
A valid message ID has an identifier, then an @ sign, and then a machine name, like so:
The official protocols on the construction of mail messages define the requirements for this format. Unfortunately, a misconfigured mail program or ISP may send out mail with bad Message-IDs, often without the machine name:
While some ISPs do not check for a malformed Message-ID header, MIT does, and bounces mail with a bad Message-ID field, with the "beader hobo" message.