Do you interpret that to mean if your family member and/or companion goes there as well? ie it doesn't have to be your merchant correct?
The place where the rules describe when a letter is considered delivered ("Your Turn", step 2.) state:
When a token (Merchant, Family Member, or Companion) is at a Place specified by one or more of your Letters, you must turn these Letters to the reverse side - they are considered "delivered". It does not matter whether or not the token was moved, and whether you turn the Letter before or after it moves.
In our first two games, we assumed a letter was delivered when any
player's token was on the corresponding numbered place, because the rule simply says "When a
token... is at Place", etc.
In playing it this way, it seems a little too powerful - quite easy to get six seals, followed by a ruby at the Secret Society. Does delivery only take place when your
token is at a place? If so, this is an area I think the rules could be clearer.