I used the IMAP library and I feel it lacks a lot of documentation regarding types and encoding.

Example:
IMAP4.list([directory[, pattern]]):
It doesn't state if it expects the directory argument to be an string (unicode) or a imap_utf7 encoded string or bytes.
It also expects names with spaces to be between double quotation marks and it doesn't state that it returns a bytes raw output.

This is valid for every function that receives a directory or mailbox argument. Also for most return values.

Documentation aside, I think it would be a nice improvement in the implementation to add an imap_utf7 convertion function, and check every directory or mailbox argument to see if it has characters outside the imap_utf7 charset and attempts to convert them automatically.

Documentation patches are welcome.  imaplib has not seen much attention for quite some time (though there is currently someone interested in working on it, so that may change).

Please open a separate issue for the utf7 enhancement proposal.

UTF-7 is tackled in https://bugs.python.org/issue5305