Dorm

It's usually most convenient to send the package to a student who lives on campus, particularly a SIPB member involved in the project that the package is for.

SOLE office

If a student dorm is not viable, send it to:

77 Massachusetts Ave
Room W20-500 (ATTN: SIPB)
Cambridge, MA
02139

Although SIPB and SOLE are at 84 Mass Ave, SOLE recommends the mailing address ought to be 77 Mass Ave.  Specify SOLE's office (W20-500), instead of SIPB's office, to minimize the chance of it going elsewhere—for example, sometimes it ends up downstairs in W20-011, which is apparently SOLE's storage space, idk, they didn't really explain it.

SOLE keeps our packages in their office on the rack.  This is preferable to having mail delivered directly outside of our door when we're not in the office, however, it comes at the cost of attachment to SOLE and less convenience (SOLE is only open weekdays till 17:00, at best).