This article is from the Food Preserving FAQ, by Eric Decker ericnospam@getcomputing.com with numerous contributions by others.
If it was made with regular pectin, high sugar recipe:
Did it jell? If it jelled, it has enough sugar, so is safe. Was it
processed? If not processed, it should be refrigerated for added
safety. Is there visible mold? If so, discard the entire contents of
the container.
If it was made with a low sugar or no sugar pectin product:
Were the directions on the box, particularly the processing or refrigeration,
followed exactly? If the directions were not followed, but there is no visible
spoilage, the product may be refrigerated, or possible frozen. If there is
mold, if there are bubbles rising, or other signs of spoilage, the product must
be discarded.
 
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