How could Colin have received letters?

A piece of regency fanfiction I was reading had Colin telling Pen in one of his letters where to address her next correspondence to because he would be travelling to that new location. And that got me thinking about the details from the show. In ep1 of season 3 we learn that Colin visited seventeen cities in four months. Ignoring any time to travel to/from home, that would be roughly a new city every seven days. A part of each of those weeks would be getting to the next location, so only actually being in a particular place for a few days. And it wasn't just different cities, it was different countries - he is asked how many places he visited when the siblings note that his gifts for them are from Spain, Italy, and France. So how much chance would there have been for anyone to send him a letter and him receive it before moving on? If they had known his travel itinerary and planned locations ahead of time, then sure. But they didn't - they are surprised to find out he traveled around as much as he did. So they didn't know his travel plans beforehand and apparently didn't get a hint of the extent of them from his letters. If he had actually told them where he'd be next in the letters and not a single one of them paid attention to where he was or where he was going then WOW, but I can't imagine they were that terrible to him to not even read his letters even if they didn't respond, so I don't think he was sharing too many forwarding addresses in his letters?

Sooo, how was he supposed to get many letters from anyone? If someone has some idea of how this used to work, or how long letters typically took to arrive, please share. And if anyone has a theory about how his family would have known where to send letters if they had wanted to (::::coughjerkscough:::). I'm just curious about the logistics when he was moving around so much in so short a time and apparently not telling his family everywhere he was going.