On various servers, I treat the junk mail folder as an incoming folder
because I don't trust the algorithms that test for email spam.
I use IMAP to check a Yahoo mail account.
I kept getting a "no such folder" checking Yahoo's junk mail folder.
I just realized that Yahoo changed the name of the junk mail folder from
"Bulk Mail" to "Bulk". I updated the entry in .pinerc so it works again
with alpine. Thunderbird users would need to make a similar change.