diff --git a/include/protocol/protocol.hpp b/include/protocol/protocol.hpp
index c13fc8c..359ab40 100644
--- a/include/protocol/protocol.hpp
+++ b/include/protocol/protocol.hpp
@@ -18,18 +18,33 @@ namespace protocol {
     using handler_t = std::function<void(protocol_t&, const message_t&)>;
     using handler_map_t = std::map<token::pattern_t, handler_t>;
 
+    struct session_key_t {
+        std::string session;
+        std::string token;
+    };
+
+    bool operator==(const session_key_t& l, const session_key_t& r);
+
+    session_key_t session_key_from(const token::list_t& tokens);
+    session_key_t session_key_from(const message_t& message);
+
     class protocol_t {
     public:
         void set_handlers(const handler_map_t handlers);
+
         void absorb(const std::string& input);
         void send(const token::list_t& tokens);
 
+        void submit_message(const session_key_t& session_key, const std::vector<std::string>& header, const std::vector<std::string>& body);
+
     protected:
         virtual void emit(const std::string& output) { };
 
     private:
         handler_map_t handlers;
         size_t max_pattern_length;
+
+        void send_data_line(const session_key_t& session_key, const std::string& data_line);
     };
 
     class ios_protocol_t : public protocol_t {
@@ -45,20 +60,11 @@ namespace protocol {
         std::ostream& out;
     };
 
-    struct session_t {
-        std::string session;
-        std::string token;
-    };
-
-    bool operator==(const session_t& l, const session_t& r);
-
-    session_t session_from(token::list_t tokens);
-    session_t session_from(message_t message);
 }
 
 namespace std {
-    template<> struct hash<protocol::session_t> {
-        std::size_t operator()(protocol::session_t const& session) const noexcept {
+    template<> struct hash<protocol::session_key_t> {
+        std::size_t operator()(protocol::session_key_t const& session) const noexcept {
             auto session_hash = std::hash<std::string>{}(session.session);
             auto token_hash = std::hash<std::string>{}(session.token);
             return session_hash ^ (token_hash << 1);
diff --git a/src/protocol/protocol.cpp b/src/protocol/protocol.cpp
index e017748..00e593a 100644
--- a/src/protocol/protocol.cpp
+++ b/src/protocol/protocol.cpp
@@ -45,6 +45,29 @@ namespace protocol {
         }
     }
 
+    void protocol_t::send_data_line(const session_key_t& session_key, const string& data_line) {
+        send({"filter-dataline", session_key.session, session_key.token, session_key.token, data_line});
+    }
+
+    void protocol_t::submit_message(const session_key_t& session_key, const vector<string>& header, const vector<string>& body) {
+        for(auto& data_line : header) {
+            send_data_line(session_key, data_line);
+        }
+
+        send_data_line(session_key, "");
+
+        for(auto& data_line : body) {
+            if(data_line == ".") {
+                send_data_line(session_key, "..");
+                continue;
+            }
+
+            send_data_line(session_key, data_line);
+        }
+
+        send_data_line(session_key, ".");
+    }
+
     ios_protocol_t::ios_protocol_t(std::istream& in, std::ostream& out) :
         in(in), out(out) { }
 
@@ -60,18 +83,18 @@ namespace protocol {
         }
     }
 
-    bool operator==(const session_t& l, const session_t& r) {
+    bool operator==(const session_key_t& l, const session_key_t& r) {
         return l.session == r.session && l.token == r.token;
     }
 
-    session_t session_from(token::list_t tokens) {
+    session_key_t session_key_from(const token::list_t& tokens) {
         auto session_id = tokens.at(5);
         auto session_token = tokens.at(6);
         return {session_id, session_token};
     }
 
-    session_t session_from(message_t message) {
+    session_key_t session_key_from(const message_t& message) {
         auto tokens = token::decompose(message.input);
-        return session_from(tokens);
+        return session_key_from(tokens);
     }
 }