Hello, I'm new here, so apologies if this belongs in one of the sub forums.

Obviously there is probably not a formal mail system for the Empire, but how to lords send new orders/letters to their subordinates in far off lands? Do they simply send a courier on horse with a sealed scroll?

Heralds who partially function mailmen as do exist. This is one of the primary duties of one of the Imperial families, the Miya who have a school, Miya Herald, focused on doing such. Within the various Clan's own lands, they would likely send an in clan courier on either foot or horse depending on urgency.

And if things are really urgent, you can get a shugenja in to either travel even faster, or send a kami to deliver it.

30 minutes ago, Tonbo Karasu said:

And if things are really urgent, you can get a shugenja in to either travel even faster, or send a kami to deliver it.

Reminder that the Bat Clan's whole gimmick in previous editions was sending messages to faraway places via magic. Their most powerful shugenja could send messages from their lands in the Mantis archipelago all the way to Toshi Ranbo and vice versa.

"Send a raven..."

By and large in Rokugan, if you need to get a message to a person who is not immediately present, you had one of three options.

1. Send a peasant messenger. Typically, this would be a dedicated servant of your household or the household you wished to contact. Often if a servant arrives with a message, they will stick around until they get a response. Depending on the importance of this message, this person may be a peasant or a samurai. This faces all the normal challenges of people crossing borders in Rokugan.
2. Give your message to a Miya Herald. The Miya Heralds travel the Imperial highway, delivering the Emperor's proclamations. This also means that their duty involves carrying any and all diplomatic mail, and they can freely travel across Clan borders. Also, they are not likely to read your mail. Supposedly. Still, it is moderately secure as bandits very rarely strike on the Imperial Highway, but it is not quite as far ranging or fast.
3. Give your message to a monk of the Barefoot Brethren of the Order of Koshin. As monks dedicated to the Fortune of Roads and Travel, the monks of Koshin can freely travel across the Empire (as no liege will bar the entry of a monk to their lands, not if they do not want to seem highly suspect), and will carry messages in exchange for simply the food they must eat on the way. This is probably the slowest of the three, but it is the least obvious and the farthest reaching.

I think that you should add omnicrone and Lorne's suggestions to that list, though.

4. Send a trained bird, such as a raven or homing pigeon. Rare, probably only works between established routes, but is a pretty good option all told.

5. Get a Shugenja to help. You either need to be really important or have a very good reason, but a Shugenja has ways to deliver messages over long distances. Worst case, they can use Domain of Suijin (I think?) to just teleport somewhere nearby. This ability is so useful, my Rokugan is likely to have temples to Suijin with suitable pools of water in important locations and have Shugenja visit them during their training, precisely so that this kind of long-range warning system is possible. It's a sacred thing, though, not to be abused frivolously.

22 minutes ago, Myrion said:

I think that you should add omnicrone and Lorne's suggestions to that list, though.

4. Send a trained bird, such as a raven or homing pigeon. Rare, probably only works between established routes, but is a pretty good option all told.

5. Get a Shugenja to help. You either need to be really important or have a very good reason, but a Shugenja has ways to deliver messages over long distances. Worst case, they can use Domain of Suijin (I think?) to just teleport somewhere nearby. This ability is so useful, my Rokugan is likely to have temples to Suijin with suitable pools of water in important locations and have Shugenja visit them during their training, precisely so that this kind of long-range warning system is possible. It's a sacred thing, though, not to be abused frivolously.

Lady shinjo's blessing allows those with it to halve travel time as well.

There is another option not yet mentioned clearly. There is, on older editions, a rank 2 air invocation, Echoes on a Breeze, which carries your words to another you know, no matter where they are in Rokugan. It meant that the winter courts were particularly important for shugenja of rank 2+

It's not in the 5E Core. I expect it will show again...

Pigeon post could probably be a Unicorn thing, it seems to have originated in the Middle East in the real world, so they might have run into some cultures who train birds that way out beyond Rokugan and brought it back. Great way to utilize the Animal Bond passion.

1 hour ago, AK_Aramis said:

There is, on older editions, a rank 2 air invocation, Echoes on a Breeze, which carries your words to another you know, no matter where they are in Rokugan.

It's rank 5 in 4e, and you must know the target.

Legacy of Kaze-no-Kami is rank 1, and creates a bird to carry a spoken message of up to a minute's length at least 10 miles.

13 hours ago, sndwurks said:

By and large in Rokugan, if you need to get a message to a person who is not immediately present, you had one of three options.

1. Send a peasant messenger. Typically, this would be a dedicated servant of your household or the household you wished to contact. Often if a servant arrives with a message, they will stick around until they get a response. Depending on the importance of this message, this person may be a peasant or a samurai. This faces all the normal challenges of people crossing borders in Rokugan.
2. Give your message to a Miya Herald. The Miya Heralds travel the Imperial highway, delivering the Emperor's proclamations. This also means that their duty involves carrying any and all diplomatic mail, and they can freely travel across Clan borders. Also, they are not likely to read your mail. Supposedly. Still, it is moderately secure as bandits very rarely strike on the Imperial Highway, but it is not quite as far ranging or fast.
3. Give your message to a monk of the Barefoot Brethren of the Order of Koshin. As monks dedicated to the Fortune of Roads and Travel, the monks of Koshin can freely travel across the Empire (as no liege will bar the entry of a monk to their lands, not if they do not want to seem highly suspect), and will carry messages in exchange for simply the food they must eat on the way. This is probably the slowest of the three, but it is the least obvious and the farthest reaching.

Several clans also had their own messengers - the Unicorn's Iuchi Courier school, for example.

Not every message can be trusted to outsiders...

Another option is, depending on urgency, that if someone is already traveling that direction, you entrust the letter to that person to either hand off to someone else trusted, or hand off to that person. That being said, there is some basic nominal assumption that if Lion-san is visiting the crab lands, and is returning home, Crab Lord can ask Lion-san to deliver some correspondance to his contact in Lion Lands when Lion-san returns home. Given that it is entrusted to him, the Lion would guard it with his or her life, and make sure it is delivered. This is, of course, based on honor. And that also assumes 1) Some form of Encryption (or that the letter actually isn't that important) and 2) It better not be something like "Attack the lion next chance you get". You can even do this with a Scorpion, but you just have to assume they will read your mail first, but pretend that they didn't, because that would be rude.