Spotting Badly Stored Wine
Degraded Seal
Indicators of spoiled wine include a corroded capsule and a sunken or raised cork. Mold growing on the outside of a bottle is generally not a cause for concern, because the ideal conditions for storing wine (a dark, humid environment) are also optimal for growing mold. However, if mold is found on the bottom of the cork, the wine is compromised.
Low Fill Level
In general, unless a bottle is 50+ years old, fill levels anywhere below the neck are a red flag. A low fill level does not always mean that a wine is flawed, but in combination with other factors, it can be a very good clue.