diff --git a/src/smtp.rs b/src/smtp.rs
new file mode 100644
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--- /dev/null
+++ b/src/smtp.rs
@@ -0,0 +1,323 @@
+// Copyright 2014 Alexis Mousset. See the COPYRIGHT
+// file at the top-level directory of this distribution.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! SMTP commands and ESMTP features library
+
+use std::io::net::ip::Port;
+
+/// Default SMTP port
+pub static SMTP_PORT: Port = 25;
+//pub static SMTPS_PORT: Port = 465;
+//pub static SUBMISSION_PORT: Port = 587;
+
+/// The word separator for SMTP transactions
+pub static SP: &'static str = " ";
+
+/// The line ending for SMTP transactions
+pub static CRLF: &'static str = "\r\n";
+
+/// A module
+pub mod smtp_command {
+    use std::fmt::{Show, Formatter, Result};
+
+    /// Supported SMTP commands
+    ///
+    /// We do not implement the following SMTP commands, as they were deprecated in RFC 5321
+    /// and must not be used by clients:
+    /// SEND, SOML, SAML, TURN
+    #[deriving(Eq,Clone)]
+    pub enum SmtpCommand<T> {
+        /// Extended Hello command
+        ExtendedHello(T),
+        /// Hello command
+        Hello(T),
+        /// Mail command, takes optionnal options
+        Mail(T, Option<Vec<T>>),
+        /// Recipient command, takes optionnal options
+        Recipient(T, Option<Vec<T>>),
+        /// Data command
+        Data,
+        /// Reset command
+        Reset,
+        /// Verify command
+        Verify(T),
+        /// Expand command
+        Expand(T),
+        /// Help command, takes optionnal options
+        Help(Option<T>),
+        /// Noop command
+        Noop,
+        /// Quit command
+        Quit,
+
+    }
+
+    impl<T: Show + Str> Show for SmtpCommand<T> {
+        fn fmt(&self, f: &mut Formatter) -> Result {
+            f.buf.write(match *self {
+                ExtendedHello(ref my_hostname) =>
+                    format!("EHLO {}", my_hostname.clone()),
+                Hello(ref my_hostname) =>
+                    format!("HELO {}", my_hostname.clone()),
+                Mail(ref from_address, None) =>
+                    format!("MAIL FROM:<{}>", from_address.clone()),
+                Mail(ref from_address, Some(ref options)) =>
+                    format!("MAIL FROM:<{}> {}", from_address.clone(), options.connect(" ")),
+                Recipient(ref to_address, None) =>
+                    format!("RCPT TO:<{}>", to_address.clone()),
+                Recipient(ref to_address, Some(ref options)) =>
+                    format!("RCPT TO:<{}> {}", to_address.clone(), options.connect(" ")),
+                Data => "DATA".to_owned(),
+                Reset => "RSET".to_owned(),
+                Verify(ref address) =>
+                    format!("VRFY {}", address.clone()),
+                Expand(ref address) =>
+                    format!("EXPN {}", address.clone()),
+                Help(None) => "HELP".to_owned(),
+                Help(Some(ref argument)) =>
+                    format!("HELP {}", argument.clone()),
+                Noop => "NOOP".to_owned(),
+                Quit => "QUIT".to_owned(),
+            }.as_bytes())
+        }
+    }
+}
+
+/// This is a module
+pub mod esmtp_parameter {
+    use std::from_str::FromStr;
+    use std::fmt::{Show, Formatter, Result};
+
+    /// Supported ESMTP keywords
+    #[deriving(Eq,Clone)]
+    pub enum EsmtpParameter {
+        /// 8BITMIME keyword
+        ///
+        /// RFC 6152 : https://tools.ietf.org/html/rfc6152
+        EightBitMime,
+        /// SIZE keyword
+        ///
+        /// RFC 1427 : https://tools.ietf.org/html/rfc1427
+        Size(uint)
+    }
+
+    impl Show for EsmtpParameter {
+        fn fmt(&self, f: &mut Formatter) -> Result {
+            f.buf.write(
+                match self {
+                    &EightBitMime   => "8BITMIME".to_owned(),
+                    &Size(ref size) => format!("SIZE={}", size)
+                }.as_bytes()
+            )
+        }
+    }
+
+    impl FromStr for EsmtpParameter {
+        fn from_str(s: &str) -> Option<EsmtpParameter> {
+            let splitted : Vec<&str> = s.splitn(' ', 1).collect();
+            match splitted.len() {
+                1 => match *splitted.get(0) {
+                         "8BITMIME" => Some(EightBitMime),
+                         _          => None
+                     },
+                2 => match (*splitted.get(0), from_str::<uint>(*splitted.get(1))) {
+                         ("SIZE", Some(size)) => Some(Size(size)),
+                         _                    => None
+                     },
+                _          => None
+            }
+        }
+    }
+
+    impl EsmtpParameter {
+        /// Checks if the ESMTP keyword is the same
+        pub fn same_keyword_as(&self, other: EsmtpParameter) -> bool {
+            if *self == other {
+                return true;
+            }
+            match (*self, other) {
+                (Size(_), Size(_)) => true,
+                _                  => false
+            }
+        }
+    }
+}
+/// This is a module
+pub mod smtp_response {
+    use std::from_str::FromStr;
+    use std::fmt::{Show, Formatter, Result};
+    use common::remove_trailing_crlf;
+    use std::result;
+
+    /// Contains an SMTP reply, with separed code and message
+    ///
+    /// We do accept messages containing only a code, to comply with RFC5321
+    #[deriving(Clone, Eq)]
+    pub struct SmtpResponse<T> {
+        /// Server response code
+        pub code: u16,
+        /// Server response string
+        pub message: Option<T>
+    }
+
+    impl<T: Show + Clone> Show for SmtpResponse<T> {
+        fn fmt(&self, f: &mut Formatter) -> Result {
+            f.buf.write(
+                match self.clone().message {
+                    Some(message) => format!("{} {}", self.code.to_str(), message),
+                    None          => self.code.to_str()
+                }.as_bytes()
+            )
+        }
+    }
+
+    // FromStr ?
+    impl FromStr for SmtpResponse<StrBuf> {
+        fn from_str(s: &str) -> Option<SmtpResponse<StrBuf>> {
+            // If the string is too short to be a response code
+            if s.len() < 3 {
+                None
+            // If we have only a code, with or without a trailing space
+            } else if s.len() == 3 || (s.len() == 4 && s.slice(3,4) == " ") {
+                match from_str::<u16>(s.slice_to(3)) {
+                    Some(code) => Some(SmtpResponse{
+                                code: code,
+                                message: None
+                            }),
+                    None         => None
+
+                }
+            // If we have a code and a message
+            } else {
+                match (
+                    from_str::<u16>(s.slice_to(3)),
+                    vec!(" ", "-").contains(&s.slice(3,4)),
+                    StrBuf::from_str(remove_trailing_crlf(s.slice_from(4).to_owned()))
+                ) {
+                    (Some(code), true, message) => Some(SmtpResponse{
+                                code: code,
+                                message: Some(message)
+                            }),
+                    _                           => None
+
+                }
+            }
+        }
+    }
+
+    impl<T: Clone> SmtpResponse<T> {
+        /// Checks the presence of the response code in the array of expected codes.
+        pub fn with_code(&self, expected_codes: Vec<u16>) -> result::Result<SmtpResponse<T>,SmtpResponse<T>> {
+            let response = self.clone();
+            if expected_codes.contains(&self.code) {
+                Ok(response)
+            } else {
+                Err(response)
+            }
+        }
+    }
+}
+
+#[cfg(test)]
+mod test {
+    use super::smtp_response::SmtpResponse;
+    use super::esmtp_parameter;
+    use super::esmtp_parameter::EsmtpParameter;
+    use super::smtp_command;
+    use super::smtp_command::SmtpCommand;
+
+    #[test]
+    fn test_command_fmt() {
+        let noop: SmtpCommand<StrBuf> = smtp_command::Noop;
+        assert_eq!(format!("{}", noop), "NOOP".to_owned());
+        assert_eq!(format!("{}", smtp_command::ExtendedHello("me")), "EHLO me".to_owned());
+        assert_eq!(format!("{}",
+            smtp_command::Mail("test", Some(vec!("option")))), "MAIL FROM:<test> option".to_owned()
+        );
+    }
+
+    #[test]
+    fn test_esmtp_parameter_same_keyword_as() {
+        assert_eq!(esmtp_parameter::EightBitMime.same_keyword_as(esmtp_parameter::EightBitMime), true);
+        assert_eq!(esmtp_parameter::Size(42).same_keyword_as(esmtp_parameter::Size(42)), true);
+        assert_eq!(esmtp_parameter::Size(42).same_keyword_as(esmtp_parameter::Size(43)), true);
+        assert_eq!(esmtp_parameter::Size(42).same_keyword_as(esmtp_parameter::EightBitMime), false);
+    }
+
+    #[test]
+    fn test_esmtp_parameter_fmt() {
+        assert_eq!(format!("{}", esmtp_parameter::EightBitMime), "8BITMIME".to_owned());
+        assert_eq!(format!("{}", esmtp_parameter::Size(42)), "SIZE=42".to_owned());
+    }
+
+    #[test]
+    fn test_esmtp_parameter_from_str() {
+        assert_eq!(from_str::<EsmtpParameter>("8BITMIME"), Some(esmtp_parameter::EightBitMime));
+        assert_eq!(from_str::<EsmtpParameter>("SIZE 42"), Some(esmtp_parameter::Size(42)));
+        assert_eq!(from_str::<EsmtpParameter>("SIZ 42"), None);
+        assert_eq!(from_str::<EsmtpParameter>("SIZE 4a2"), None);
+        // TODO: accept trailing spaces ?
+        assert_eq!(from_str::<EsmtpParameter>("SIZE 42 "), None);
+    }
+
+    #[test]
+    fn test_smtp_response_fmt() {
+        assert_eq!(format!("{}", SmtpResponse{code: 200, message: Some("message")}), "200 message".to_owned());
+    }
+
+    #[test]
+    fn test_smtp_response_from_str() {
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("200 response message"),
+            Some(SmtpResponse{
+                code: 200,
+                message: Some(StrBuf::from_str("response message"))
+            })
+        );
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("200-response message"),
+            Some(SmtpResponse{
+                code: 200,
+                message: Some(StrBuf::from_str("response message"))
+            })
+        );
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("200"),
+            Some(SmtpResponse{
+                code: 200,
+                message: None
+            })
+        );
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("200 "),
+            Some(SmtpResponse{
+                code: 200,
+                message: None
+            })
+        );
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("200-response\r\nmessage"),
+            Some(SmtpResponse{
+                code: 200,
+                message: Some(StrBuf::from_str("response\r\nmessage"))
+            })
+        );
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("2000response message"), None);
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("20a response message"), None);
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("20 "), None);
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("20"), None);
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>("2"), None);
+        assert_eq!(from_str::<SmtpResponse<StrBuf>>(""), None);
+    }
+
+    #[test]
+    fn test_smtp_response_with_code() {
+        assert_eq!(SmtpResponse{code: 200, message: Some("message")}.with_code(vec!(200)),
+            Ok(SmtpResponse{code: 200, message: Some("message")}));
+        assert_eq!(SmtpResponse{code: 400, message: Some("message")}.with_code(vec!(200)),
+            Err(SmtpResponse{code: 400, message: Some("message")}));
+        assert_eq!(SmtpResponse{code: 200, message: Some("message")}.with_code(vec!(200, 300)),
+            Ok(SmtpResponse{code: 200, message: Some("message")}));
+    }
+}