How can I browse the contents of a Berkeley DB file?

Question

I'd like to see what's in a bdb file in my Thunderbird profile:

$ file key3.db
key3.db: Berkeley DB 1.85 (Hash, version 2, native byte-order)

I've tried this and it doesn't seem to work:

$ db_dump -l key3.db 
db_dump: key3.db: unexpected file type or format
db_dump: open: key3.db: Invalid argument

$ db_dump -V
Berkeley DB 4.7.25: (May 15, 2008)

Any suggestions?