+ (> (gnus-data-number datum) 0)
+ (not (memq (gnus-data-number datum) gnus-newsgroup-unreads))
+ (not (= (gnus-data-mark datum) gnus-canceled-mark))
+ (setq msgid (mail-header-id (gnus-data-header datum)))
+ (not (nnheader-fake-message-id-p msgid))
+ (not (intern-soft msgid gnus-dup-hashtb)))
+ (push msgid gnus-dup-list)
+ (intern msgid gnus-dup-hashtb))))