Voice message birds (ordonanzes) - no, but magic letter can pass into another duchie. They do pass through the duchy gate, though, and may be checked by the border guard.
Man, it seems like such a loss, that song texts are not placed into manga translation. It is visible and pretty much spelled out that characters are in conversation with each other through the song. Except we don't see what they say :(
While Rozemyne is an official translation, I find it amusing, that German word for a rose (I guess it was supposed to be the flower in the name) is "die Rose". But the "z" sound you expect is still there. Generally, german "s" sounds like "z" in pairs of s+vowel.
You're absolutely right, the one I was thinking about is the first visit from earlier - and it was already in manga, entire chapter 21 for that event. I just forgot.
This chapter shows another of Tuuli and Effa's visits from P3V3, "The Start of Winter Socializing".
Oh, man - Tuuli and Myne's mother was finally able to attend audience with Rozemyne to deliver orders, but couldn't almost say anything. Only 4 pages for the whole event.
Welp, I guess manga is portraying how secretive they have to be. Barely any interaction, only Rozemyne looking wistfully out...