diff --git a/lettre/Cargo.toml b/lettre/Cargo.toml
index 0d3f1b7..503a261 100644
--- a/lettre/Cargo.toml
+++ b/lettre/Cargo.toml
@@ -24,10 +24,7 @@ nom = { version = "^3.2", optional = true }
 bufstream = { version = "^0.1", optional = true }
 native-tls = { version = "^0.1", optional = true }
 base64 = { version = "^0.9", optional = true }
-hex = { version = "^0.3", optional = true }
 hostname = { version = "^0.1", optional = true }
-md-5 = { version = "^0.7", optional = true }
-hmac = { version = "^0.6", optional = true }
 serde = { version = "^1.0", optional = true }
 serde_json = { version = "^1.0", optional = true }
 serde_derive = { version = "^1.0", optional = true }
@@ -41,7 +38,6 @@ default = ["file-transport", "smtp-transport", "sendmail-transport"]
 unstable = []
 serde-impls = ["serde", "serde_derive"]
 file-transport = ["serde-impls", "serde_json"]
-crammd5-auth = ["md-5", "hmac", "hex"]
 smtp-transport = ["bufstream", "native-tls", "base64", "nom", "hostname"]
 sendmail-transport = []
 
diff --git a/lettre/src/lib.rs b/lettre/src/lib.rs
index b120073..07a22cb 100644
--- a/lettre/src/lib.rs
+++ b/lettre/src/lib.rs
@@ -10,16 +10,10 @@
 extern crate base64;
 #[cfg(feature = "smtp-transport")]
 extern crate bufstream;
-#[cfg(feature = "crammd5-auth")]
-extern crate hex;
-#[cfg(feature = "crammd5-auth")]
-extern crate hmac;
 #[cfg(feature = "smtp-transport")]
 extern crate hostname;
 #[macro_use]
 extern crate log;
-#[cfg(feature = "crammd5-auth")]
-extern crate md5;
 #[cfg(feature = "smtp-transport")]
 extern crate native_tls;
 #[cfg(feature = "smtp-transport")]
diff --git a/lettre/src/smtp/authentication.rs b/lettre/src/smtp/authentication.rs
index 1a359b7..589f909 100644
--- a/lettre/src/smtp/authentication.rs
+++ b/lettre/src/smtp/authentication.rs
@@ -1,31 +1,14 @@
-//! Provides authentication mechanisms
+//! Provides limited SASL authentication mechanisms
 
-#[cfg(feature = "crammd5-auth")]
-use md5::Md5;
-#[cfg(feature = "crammd5-auth")]
-use hmac::{Hmac, Mac};
-#[cfg(feature = "crammd5-auth")]
-use hex;
 use smtp::NUL;
 use smtp::error::Error;
 use std::fmt::{self, Display, Formatter};
 
 /// Accepted authentication mechanisms on an encrypted connection
 /// Trying LOGIN last as it is deprecated.
-#[cfg(feature = "crammd5-auth")]
-pub const DEFAULT_ENCRYPTED_MECHANISMS: &[Mechanism] =
-    &[Mechanism::Plain, Mechanism::CramMd5, Mechanism::Login];
-/// Accepted authentication mechanisms on an encrypted connection
-/// Trying LOGIN last as it is deprecated.
-#[cfg(not(feature = "crammd5-auth"))]
 pub const DEFAULT_ENCRYPTED_MECHANISMS: &[Mechanism] = &[Mechanism::Plain, Mechanism::Login];
 
 /// Accepted authentication mechanisms on an unencrypted connection
-#[cfg(feature = "crammd5-auth")]
-pub const DEFAULT_UNENCRYPTED_MECHANISMS: &[Mechanism] = &[Mechanism::CramMd5];
-/// Accepted authentication mechanisms on an unencrypted connection
-/// When CRAMMD5 support is not enabled, no mechanisms are allowed.
-#[cfg(not(feature = "crammd5-auth"))]
 pub const DEFAULT_UNENCRYPTED_MECHANISMS: &[Mechanism] = &[];
 
 /// Convertable to user credentials
@@ -51,14 +34,14 @@ impl<S: Into<String>, T: Into<String>> IntoCredentials for (S, T) {
 #[derive(PartialEq, Eq, Clone, Hash, Debug)]
 #[cfg_attr(feature = "serde-impls", derive(Serialize, Deserialize))]
 pub struct Credentials {
-    username: String,
-    password: String,
+    authentication_identity: String,
+    secret: String,
 }
 
 impl Credentials {
     /// Create a `Credentials` struct from username and password
     pub fn new(username: String, password: String) -> Credentials {
-        Credentials { username, password }
+        Credentials { authentication_identity: username, secret: password }
     }
 }
 
@@ -73,10 +56,6 @@ pub enum Mechanism {
     /// Obsolete but needed for some providers (like office365)
     /// https://www.ietf.org/archive/id/draft-murchison-sasl-login-00.txt
     Login,
-    /// CRAM-MD5 authentication mechanism
-    /// RFC 2195: https://tools.ietf.org/html/rfc2195
-    #[cfg(feature = "crammd5-auth")]
-    CramMd5,
 }
 
 impl Display for Mechanism {
@@ -87,8 +66,6 @@ impl Display for Mechanism {
             match *self {
                 Mechanism::Plain => "PLAIN",
                 Mechanism::Login => "LOGIN",
-                #[cfg(feature = "crammd5-auth")]
-                Mechanism::CramMd5 => "CRAM-MD5",
             }
         )
     }
@@ -101,8 +78,6 @@ impl Mechanism {
         match *self {
             Mechanism::Plain => true,
             Mechanism::Login => false,
-            #[cfg(feature = "crammd5-auth")]
-            Mechanism::CramMd5 => false,
         }
     }
 
@@ -118,7 +93,7 @@ impl Mechanism {
                 Some(_) => Err(Error::Client("This mechanism does not expect a challenge")),
                 None => Ok(format!(
                     "{}{}{}{}",
-                    NUL, credentials.username, NUL, credentials.password
+                    NUL, credentials.authentication_identity, NUL, credentials.secret
                 )),
             },
             Mechanism::Login => {
@@ -128,32 +103,15 @@ impl Mechanism {
                 };
 
                 if vec!["User Name", "Username:", "Username"].contains(&decoded_challenge) {
-                    return Ok(credentials.username.to_string());
+                    return Ok(credentials.authentication_identity.to_string());
                 }
 
                 if vec!["Password", "Password:"].contains(&decoded_challenge) {
-                    return Ok(credentials.password.to_string());
+                    return Ok(credentials.secret.to_string());
                 }
 
                 Err(Error::Client("Unrecognized challenge"))
             }
-            #[cfg(feature = "crammd5-auth")]
-            Mechanism::CramMd5 => {
-                let decoded_challenge = match challenge {
-                    Some(challenge) => challenge,
-                    None => return Err(Error::Client("This mechanism does expect a challenge")),
-                };
-
-                let mut hmac: Hmac<Md5> = Hmac::new_varkey(credentials.password.as_bytes())
-                    .expect("md5 should support variable key size");
-                hmac.input(decoded_challenge.as_bytes());
-
-                Ok(format!(
-                    "{} {}",
-                    credentials.username,
-                    hex::encode(hmac.result().code())
-                ))
-            }
         }
     }
 }
@@ -191,23 +149,4 @@ mod test {
         );
         assert!(mechanism.response(&credentials, None).is_err());
     }
-
-    #[test]
-    #[cfg(feature = "crammd5-auth")]
-    fn test_cram_md5() {
-        let mechanism = Mechanism::CramMd5;
-
-        let credentials = Credentials::new("alice".to_string(), "wonderland".to_string());
-
-        assert_eq!(
-            mechanism
-                .response(
-                    &credentials,
-                    Some("PDE3ODkzLjEzMjA2NzkxMjNAdGVzc2VyYWN0LnN1c2FtLmluPg==")
-                )
-                .unwrap(),
-            "alice a540ebe4ef2304070bbc3c456c1f64c0"
-        );
-        assert!(mechanism.response(&credentials, None).is_err());
-    }
 }
diff --git a/lettre/src/smtp/commands.rs b/lettre/src/smtp/commands.rs
index 9052a14..9f3762a 100644
--- a/lettre/src/smtp/commands.rs
+++ b/lettre/src/smtp/commands.rs
@@ -313,8 +313,6 @@ impl AuthCommand {
 mod test {
     use super::*;
     use smtp::extension::MailBodyParameter;
-    #[cfg(feature = "crammd5-auth")]
-    use smtp::response::{Category, Code, Detail, Severity};
 
     #[test]
     fn test_display() {
@@ -391,18 +389,6 @@ mod test {
             ),
             "AUTH PLAIN AHVzZXIAcGFzc3dvcmQ=\r\n"
         );
-        #[cfg(feature = "crammd5-auth")]
-        assert_eq!(
-            format!(
-                "{}",
-                AuthCommand::new(
-                    Mechanism::CramMd5,
-                    credentials.clone(),
-                    Some("test".to_string()),
-                ).unwrap()
-            ),
-            "dXNlciAzMTYxY2NmZDdmMjNlMzJiYmMzZTQ4NjdmYzk0YjE4Nw==\r\n"
-        );
         assert_eq!(
             format!(
                 "{}",
@@ -410,24 +396,5 @@ mod test {
             ),
             "AUTH LOGIN\r\n"
         );
-        #[cfg(feature = "crammd5-auth")]
-        assert_eq!(
-            format!(
-                "{}",
-                AuthCommand::new_from_response(
-                    Mechanism::CramMd5,
-                    credentials.clone(),
-                    &Response::new(
-                        Code::new(
-                            Severity::PositiveIntermediate,
-                            Category::Unspecified3,
-                            Detail::Four,
-                        ),
-                        vec!["dGVzdAo=".to_string()],
-                    ),
-                ).unwrap()
-            ),
-            "dXNlciA1NTIzNThiMzExOWFjOWNkYzM2YWRiN2MxNWRmMWJkNw==\r\n"
-        );
     }
 }
diff --git a/lettre/src/smtp/extension.rs b/lettre/src/smtp/extension.rs
index 1ddab70..b4fba39 100644
--- a/lettre/src/smtp/extension.rs
+++ b/lettre/src/smtp/extension.rs
@@ -145,10 +145,6 @@ impl ServerInfo {
                         "LOGIN" => {
                             features.insert(Extension::Authentication(Mechanism::Login));
                         }
-                        #[cfg(feature = "crammd5-auth")]
-                        "CRAM-MD5" => {
-                            features.insert(Extension::Authentication(Mechanism::CramMd5));
-                        }
                         _ => (),
                     }
                 },
@@ -357,8 +353,6 @@ mod test {
 
         assert!(server_info.supports_feature(Extension::EightBitMime));
         assert!(!server_info.supports_feature(Extension::StartTls));
-        #[cfg(feature = "crammd5-auth")]
-        assert!(!server_info.supports_auth_mechanism(Mechanism::CramMd5));
 
         let response2 = Response::new(
             Code::new(
@@ -377,8 +371,6 @@ mod test {
         let mut features2 = HashSet::new();
         assert!(features2.insert(Extension::EightBitMime));
         assert!(features2.insert(Extension::Authentication(Mechanism::Plain),));
-        #[cfg(feature = "crammd5-auth")]
-        assert!(features2.insert(Extension::Authentication(Mechanism::CramMd5),));
 
         let server_info2 = ServerInfo {
             name: "me".to_string(),
@@ -389,8 +381,6 @@ mod test {
 
         assert!(server_info2.supports_feature(Extension::EightBitMime));
         assert!(server_info2.supports_auth_mechanism(Mechanism::Plain));
-        #[cfg(feature = "crammd5-auth")]
-        assert!(server_info2.supports_auth_mechanism(Mechanism::CramMd5));
         assert!(!server_info2.supports_feature(Extension::StartTls));
     }
 }
diff --git a/lettre/src/smtp/mod.rs b/lettre/src/smtp/mod.rs
index b99172b..4d6d84f 100644
--- a/lettre/src/smtp/mod.rs
+++ b/lettre/src/smtp/mod.rs
@@ -8,8 +8,7 @@
 //! It implements the following extensions:
 //!
 //! * 8BITMIME ([RFC 6152](https://tools.ietf.org/html/rfc6152))
-//! * AUTH ([RFC 4954](http://tools.ietf.org/html/rfc4954)) with PLAIN, LOGIN and
-//! CRAM-MD5 mechanisms
+//! * AUTH ([RFC 4954](http://tools.ietf.org/html/rfc4954)) with PLAIN, LOGIN mechanisms
 //! * STARTTLS ([RFC 2487](http://tools.ietf.org/html/rfc2487))
 //! * SMTPUTF8 ([RFC 6531](http://tools.ietf.org/html/rfc6531))
 //!