As you've probably figured out by now, I am really into the details. A lot of times, if you look hard enough, you'll find little easter eggs that the cast, crew or writers have built into a scene or script if you're paying careful attention.
It wasn't until the show had been off for a while and I was missing my Postables that I started re-watching episodes and becoming keen to these little things. I thought Holly's letter might fall under the easter egg category. So, when I saw Holly's full address in "A Hope & A Future," it wasn't long before I decided to Google it!
Except this address location---actually this whole part of the city---is not residential, but houses the Parisian City Government. That means, at least in the real world, Holly was apparently living in a government building! How do you sign a three year lease for that? Better yet, how do you get mail delivered to you there?!
If you do a Google street view, I am happy to report that it's actually rather beautiful and you would probably would want to live in the immediate area if it wasn't a government hub.
Oddly enough, it seems that by the time we get to From Paris With Love, Holly has apparently moved. So much for that three year lease! The address is in a completely different zip code---literally.
But don't get too excited about her moving out of the government building just yet, because when you try and put that new address into any search engine, it wastes no time telling you that it doesn't exist!
It begs the question: Where was that mailbox she got Oliver's letter from located?
Did someone forget the original address? Why change it? At least the first address led you to a real place!
So, in a strange twist of fate, it appears that Oliver's letter was, in a way, always destined to return to the DLO!
Between a real address in a non-residential area, and a second address that simply doesn't exist, even if Oliver hadn't damaged the letter himself by getting it wet, I suppose, at least in the real world, it wouldn't have made it to its intended destination anyway.
I guess the fact the letter finally did make it to Holly is simply the magic of television! Or perhaps it was an act of divine intervention?
And now you know all the quirks related to Holly's letter!
Always Looking For More,
P.S. I still don't know where Holly is/was...let me know if you find her/figure it out!