+group/function elements."
+ :group 'nnimap
+ :type '(choice :tag "Rule type"
+ (repeat :menu-tag "Single-server"
+ :tag "Single-server list"
+ (list (string :tag "Mailbox")
+ (choice :tag "Predicate"
+ (regexp :tag "A regexp")
+ (nnimap-strict-function :tag "A function"))))
+ (choice :menu-tag "A function"
+ :tag "A function"
+ (function-item nnimap-split-fancy)
+ (function-item nnmail-split-fancy)
+ (nnimap-strict-function :tag "User-defined function"))
+ (repeat :menu-tag "Multi-server (extended)"
+ :tag "Multi-server list"
+ (list (regexp :tag "Server regexp")
+ (list (regexp :tag "Incoming Mailbox regexp")
+ (repeat :tag "Rules for matching server(s) and mailbox(es)"
+ (list (string :tag "Destination mailbox")
+ (choice :tag "Predicate"
+ (regexp :tag "A Regexp")
+ (nnimap-strict-function :tag "A Function")))))))))
+
+(defcustom nnimap-split-predicate "UNSEEN UNDELETED"