Overview
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The Trade Office is unlocked at level 41. This structure allows you to send out and receive caravans to/from other players.
You start with 50 caravans to send and room to receive 100. Each Trade Office level adds 1 to send and 2 to receive.
In-depth
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No matter how many caravans you possess, you always send 1/4 of your maximum when trading with a player. A player with 100 caravans will always send out 25 per trade.
In order to alert other players that you're ready and able to trade, there is a button on the right side of the Trade
Office interface that enters a message with a "Trade" link ready to be posted in your desired chat channel.
When a player clicks the Trade link, it automatically sends the caravans to the player that posted the message. This player must then Accept the caravans manually and is prompted to send caravans in return.
Be courteous when trading
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You can have many players waiting for you to receive their caravans, but you can only have one pending trade going out at a time.
The amount of caravans you can receive is always double that of the amount you can send. The amount you can send is determined by the Trade Office level.
You receive much more silver for sending out caravans than you
If you cannot accept caravans, do not leave it there pending. Manually reject the trade instead of leaving the player waiting. Do not worry about telling them you cannot receive, just click reject as they're waiting to send out more caravans.