diff --git a/lib/nntp/tiny/mbox.py b/lib/nntp/tiny/mbox.py
index 981c609..af6a9f9 100644
--- a/lib/nntp/tiny/mbox.py
+++ b/lib/nntp/tiny/mbox.py
@@ -62,23 +62,26 @@ class MBoxMessageState(enum.Enum):
     BODY   = 2
 
 class MBoxMessage():
-    __slots__ = 'state', 'headers', 'line', 'body', 'key',
+    __slots__ = 'state', 'headers', 'line', 'content', 'body', 'key',
 
     def __init__(self):
         self.state   = MBoxMessageState.EMPTY
         self.headers = dict()
         self.line    = None
-        self.body    = ''
+        self.content = ''
+        self.body    = None
         self.key     = None
 
     def add(self, line: str):
+        if self.line is not None:
+            self.content += self.line
+
         if self.state is MBoxMessageState.EMPTY:
             self.state = MBoxMessageState.HEADER
 
         if self.state is MBoxMessageState.HEADER:
             if line == '\n' or line == '\r\n':
                 self.state = MBoxMessageState.BODY
-                self.body  = ''
             elif line[0] == ' ' or line[0] == '\t':
                 self.headers[self.key] += ' ' + line.strip()
             else:
@@ -89,15 +92,15 @@ class MBoxMessage():
 
                     self.headers[self.key] = match[2].rstrip()
         elif self.state is MBoxMessageState.BODY:
-            if self.line is None:
-                self.body = line
+            if self.body is None:
+                self.body = ''
             else:
                 self.body += self.line
 
-            self.line = line
+        self.line = line
 
     def is_first_line(self):
-        return len(self.headers) == 1 and self.body == ''
+        return len(self.headers) == 1 and (self.body == '' or self.body is None)
 
     @staticmethod
     def each_line(text: str):