+# only used by NNTP, so we need ->mm anyways
+sub art_min { $_[0]->{-art_min} //= eval { $_[0]->mm(1)->min } }
+
+# used by IMAP, too, which tries to avoid ->mm (but ->{mm} is likely
+# faster since it's smaller iff available)
+sub art_max {
+ $_[0]->{-art_max} //= eval { $_[0]->{mm}->max } //
+ eval { $_[0]->over(1)->max };
+}
+