[7898] Improve client error output at different mail send errors, cleanup code.

src/game/SharedDefines.h

@@ -2512,4 +2512,32 @@ enum BattleGroundTypeId
 };
 #define MAX_BATTLEGROUND_TYPE_ID 12
 
+enum MailResponseType
+{
+    MAIL_SEND               = 0,
+    MAIL_MONEY_TAKEN        = 1,
+    MAIL_ITEM_TAKEN         = 2,
+    MAIL_RETURNED_TO_SENDER = 3,
+    MAIL_DELETED            = 4,
+    MAIL_MADE_PERMANENT     = 5
+};
+
+enum MailResponseResult
+{
+    MAIL_OK                            = 0,
+    MAIL_ERR_EQUIP_ERROR               = 1,
+    MAIL_ERR_CANNOT_SEND_TO_SELF       = 2,
+    MAIL_ERR_NOT_ENOUGH_MONEY          = 3,
+    MAIL_ERR_RECIPIENT_NOT_FOUND       = 4,
+    MAIL_ERR_NOT_YOUR_TEAM             = 5,
+    MAIL_ERR_INTERNAL_ERROR            = 6,
+    MAIL_ERR_DISABLED_FOR_TRIAL_ACC    = 14,
+    MAIL_ERR_RECIPIENT_CAP_REACHED     = 15,
+    MAIL_ERR_CANT_SEND_WRAPPED_COD     = 16,
+    MAIL_ERR_MAIL_AND_CHAT_SUSPENDED   = 17,
+    MAIL_ERR_TOO_MANY_ATTACHMENTS      = 18,
+    MAIL_ERR_MAIL_ATTACHMENT_INVALID   = 19,
+    MAIL_ERR_ITEM_HAS_EXPIRED          = 21,
+};
+
 #endif