Ruby 1.8.7 リファレンスマニュアル > ライブラリ一覧 > net/imapライブラリ > Net::IMAPクラス > lsub
lsub(refname, mailbox)
Sends a LSUB command, and returns a subset of names from the set of names that the user has declared as being "active" or "subscribed". The return value is an array of Net::IMAP::MailboxList.