Newspapers often published lists of unclaimed letters in the local post office. Think about what appearing on that list means about your ancestor:
- someone thought your ancestor lived in that location when they mailed the letter
- the person lived near enough that post office so that sending a letter there made sense
Your ancestor could also have been dead by the time his name was published in the paper on the list of unclaimed letters. Appearing on the list is not hard evidence that he was alive on the publication date
Your ancestor probably did live in that location when the letter was sent. But, if their name on that list is inconsistent with other known information, there could be a very plausible explanation.