Doc pass

dependencies.gradle

@@ -9,5 +9,6 @@ dependencies {
     compileOnly('com.github.GTNewHorizons:BuildCraft:7.1.57:api')
     compileOnly('net.industrial-craft:industrialcraft-2:2.2.828-experimental:dev')
     compileOnly('curse.maven:craftguide-75557:2459320')
+    compileOnly('com.github.GTNewHorizons:Postea:1.4.0-mu:dev')
     devOnlyNonPublishable('net.xonich.mc:NoHotbarNeeded:0.0.3:dev')
 }

src/main/java/forestry/core/utils/PosteaCompat.java

@@ -0,0 +1,41 @@
+package forestry.core.utils;
+
+import com.gtnewhorizons.postea.api.IVersionedTransformer;
+import net.minecraft.nbt.NBTTagCompound;
+
+import com.gtnewhorizons.postea.api.CustomDataReplacementManager;
+
+import cpw.mods.fml.common.Loader;
+
+/// Used to provide custom save data (like mail boxes) to Postea's [IVersionedTransformer]s.
+///
+/// These transformers allow other mods to change saved data based on their own version stamps. This compat flags,
+/// to those transformers, the times they should fire. [#transform] is used before consuming data, so the transformer
+/// can run, and [#stamp] is used for fresh data to ensure the transformer can add a stamp of its current version.
+public final class PosteaCompat {
+
+    private static final boolean POSTEA = Loader.isModLoaded("postea");
+
+    private PosteaCompat() {}
+
+    /// Transforms a root read from disk in place; call before consuming it.
+    public static void transform(String storageId, NBTTagCompound root) {
+        if (POSTEA) Impl.transform(storageId, root);
+    }
+
+    /// Stamps a freshly built root about to be written to disk.
+    public static void stamp(NBTTagCompound root) {
+        if (POSTEA) Impl.stamp(root);
+    }
+
+    private static final class Impl {
+
+        static void transform(String storageId, NBTTagCompound root) {
+            CustomDataReplacementManager.transform(storageId, root);
+        }
+
+        static void stamp(NBTTagCompound root) {
+            CustomDataReplacementManager.stamp(root);
+        }
+    }
+}

src/main/java/forestry/mail/POBox.java

@@ -19,6 +19,7 @@ import forestry.api.mail.IMailAddress;
 import forestry.api.mail.PostManager;
 import forestry.core.inventory.InventoryAdapter;
 import forestry.core.utils.InventoryUtil;
+import forestry.core.utils.PosteaCompat;
 
 public class POBox extends WorldSavedData implements IInventory {
 
@@ -42,6 +43,7 @@ public class POBox extends WorldSavedData implements IInventory {
 
     @Override
     public void readFromNBT(NBTTagCompound nbttagcompound) {
+        PosteaCompat.transform("forestry:" + mapName, nbttagcompound);
         if (nbttagcompound.hasKey("address")) {
             this.address = MailAddress.loadFromNBT(nbttagcompound.getCompoundTag("address"));
         }
@@ -56,6 +58,7 @@ public class POBox extends WorldSavedData implements IInventory {
             nbttagcompound.setTag("address", nbt);
         }
         letters.writeToNBT(nbttagcompound);
+        PosteaCompat.stamp(nbttagcompound);
     }
 
     public boolean storeLetter(ItemStack letterstack) {