diff --git a/lisp/nnmail.el b/lisp/nnmail.el
index c86e96b..00de781 100644
--- a/lisp/nnmail.el
+++ b/lisp/nnmail.el
@@ -1389,6 +1389,10 @@ See the documentation for the variable `nnmail-split-fancy' for details."
      ((null split)
       nil)
 
+     ;; t split
+     ((eq split t)
+      (list t))
+
      ;; A group name.  Do the \& and \N subs into the string.
      ((stringp split)
       (when nnmail-split-tracing
@@ -1401,6 +1405,28 @@ See the documentation for the variable `nnmail-split-fancy' for details."
 	(push "junk" nnmail-split-trace))
       (list 'junk))
 
+     ;; Logical OR operation.
+     ((eq (car split) 'or)
+      (let (done
+            (clauses (cadr split))
+            (split (cddr split)))
+        (while (and (not done) (car clauses))
+          (setq done (car (nnmail-split-it (car clauses)))
+                clauses (cdr clauses)))
+        (when done
+          (nnmail-split-it (car split)))))
+
+     ;; Logical AND operation.
+     ((eq (car split) 'and)
+      (let ((done t)
+            (clauses (cadr split))
+            (split (cddr split)))
+        (while (and done (car clauses))
+          (setq done (car (nnmail-split-it (car clauses)))
+                clauses (cdr clauses)))
+        (when (and done (null clauses))
+          (nnmail-split-it (car split)))))
+
      ;; Builtin & operation.
      ((eq (car split) '&)
       (apply 'nconc (mapcar 'nnmail-split-it (cdr split))))