diff --git a/src/vmime/net/imap/IMAPConnection.cpp b/src/vmime/net/imap/IMAPConnection.cpp
index 5e6f6f8f..04705f6c 100644
--- a/src/vmime/net/imap/IMAPConnection.cpp
+++ b/src/vmime/net/imap/IMAPConnection.cpp
@@ -355,7 +355,26 @@ void IMAPConnection::authenticateSASL()
 
 		saslSession->init();
 
-		send(true, "AUTHENTICATE " + mech->getName(), true);
+		std::ostringstream cmd;
+		cmd << "AUTHENTICATE " << mech->getName();
+
+		if (saslSession->getMechanism()->hasInitialResponse())
+		{
+			byte_t* initialResp = 0;
+			size_t initialRespLen = 0;
+
+			saslSession->evaluateChallenge(NULL, 0, &initialResp, &initialRespLen);
+
+			string encodedInitialResp(saslContext->encodeB64(initialResp, initialRespLen));
+			delete [] initialResp;
+
+			if (encodedInitialResp.empty())
+				cmd << " =";
+			else
+				cmd << " " << encodedInitialResp;
+		}
+
+		send(true, cmd.str(), true);
 
 		for (bool cont = true ; cont ; )
 		{
diff --git a/src/vmime/net/pop3/POP3Command.cpp b/src/vmime/net/pop3/POP3Command.cpp
index 6fe301ce..3c544fc0 100644
--- a/src/vmime/net/pop3/POP3Command.cpp
+++ b/src/vmime/net/pop3/POP3Command.cpp
@@ -73,6 +73,17 @@ shared_ptr <POP3Command> POP3Command::AUTH(const string& mechName)
 }
 
 
+// static
+shared_ptr <POP3Command> POP3Command::AUTH(const string& mechName, const string& initialResponse)
+{
+	std::ostringstream cmd;
+	cmd.imbue(std::locale::classic());
+	cmd << "AUTH " << mechName << " " << initialResponse;
+
+	return createCommand(cmd.str());
+}
+
+
 // static
 shared_ptr <POP3Command> POP3Command::STLS()
 {
diff --git a/src/vmime/net/pop3/POP3Command.hpp b/src/vmime/net/pop3/POP3Command.hpp
index cc3c4fd5..e34e4e2b 100644
--- a/src/vmime/net/pop3/POP3Command.hpp
+++ b/src/vmime/net/pop3/POP3Command.hpp
@@ -57,6 +57,7 @@ public:
 	static shared_ptr <POP3Command> CAPA();
 	static shared_ptr <POP3Command> NOOP();
 	static shared_ptr <POP3Command> AUTH(const string& mechName);
+	static shared_ptr <POP3Command> AUTH(const string& mechName, const string& initialResponse);
 	static shared_ptr <POP3Command> STLS();
 	static shared_ptr <POP3Command> APOP(const string& username, const string& digest);
 	static shared_ptr <POP3Command> USER(const string& username);
diff --git a/src/vmime/net/pop3/POP3Connection.cpp b/src/vmime/net/pop3/POP3Connection.cpp
index f5a1a448..45c668f5 100644
--- a/src/vmime/net/pop3/POP3Connection.cpp
+++ b/src/vmime/net/pop3/POP3Connection.cpp
@@ -446,7 +446,29 @@ void POP3Connection::authenticateSASL()
 
 		saslSession->init();
 
-		POP3Command::AUTH(mech->getName())->send(dynamicCast <POP3Connection>(shared_from_this()));
+		shared_ptr <POP3Command> authCmd;
+
+		if (saslSession->getMechanism()->hasInitialResponse())
+		{
+			byte_t* initialResp = 0;
+			size_t initialRespLen = 0;
+
+			saslSession->evaluateChallenge(NULL, 0, &initialResp, &initialRespLen);
+
+			string encodedInitialResp(saslContext->encodeB64(initialResp, initialRespLen));
+			delete [] initialResp;
+
+			if (encodedInitialResp.empty())
+				authCmd = POP3Command::AUTH(mech->getName(), "=");
+			else
+				authCmd = POP3Command::AUTH(mech->getName(), encodedInitialResp);
+		}
+		else
+		{
+			authCmd = POP3Command::AUTH(mech->getName());
+		}
+
+		authCmd->send(dynamicCast <POP3Connection>(shared_from_this()));
 
 		for (bool cont = true ; cont ; )
 		{
diff --git a/src/vmime/net/smtp/SMTPCommand.cpp b/src/vmime/net/smtp/SMTPCommand.cpp
index 949ab0c1..2120caf5 100644
--- a/src/vmime/net/smtp/SMTPCommand.cpp
+++ b/src/vmime/net/smtp/SMTPCommand.cpp
@@ -79,6 +79,17 @@ shared_ptr <SMTPCommand> SMTPCommand::AUTH(const string& mechName)
 }
 
 
+// static
+shared_ptr <SMTPCommand> SMTPCommand::AUTH(const string& mechName, const std::string& initialResponse)
+{
+	std::ostringstream cmd;
+	cmd.imbue(std::locale::classic());
+	cmd << "AUTH " << mechName << " " << initialResponse;
+
+	return createCommand(cmd.str());
+}
+
+
 // static
 shared_ptr <SMTPCommand> SMTPCommand::STARTTLS()
 {
diff --git a/src/vmime/net/smtp/SMTPCommand.hpp b/src/vmime/net/smtp/SMTPCommand.hpp
index dbb0888b..a5b8cca5 100644
--- a/src/vmime/net/smtp/SMTPCommand.hpp
+++ b/src/vmime/net/smtp/SMTPCommand.hpp
@@ -60,6 +60,7 @@ public:
 	static shared_ptr <SMTPCommand> HELO(const string& hostname);
 	static shared_ptr <SMTPCommand> EHLO(const string& hostname);
 	static shared_ptr <SMTPCommand> AUTH(const string& mechName);
+	static shared_ptr <SMTPCommand> AUTH(const string& mechName, const std::string& initialResponse);
 	static shared_ptr <SMTPCommand> STARTTLS();
 	static shared_ptr <SMTPCommand> MAIL(const mailbox& mbox, const bool utf8);
 	static shared_ptr <SMTPCommand> MAIL(const mailbox& mbox, const bool utf8, const size_t size);
diff --git a/src/vmime/net/smtp/SMTPConnection.cpp b/src/vmime/net/smtp/SMTPConnection.cpp
index a45f9149..4985b563 100644
--- a/src/vmime/net/smtp/SMTPConnection.cpp
+++ b/src/vmime/net/smtp/SMTPConnection.cpp
@@ -367,7 +367,25 @@ void SMTPConnection::authenticateSASL()
 
 		saslSession->init();
 
-		sendRequest(SMTPCommand::AUTH(mech->getName()));
+		if (saslSession->getMechanism()->hasInitialResponse())
+		{
+			byte_t* initialResp = 0;
+			size_t initialRespLen = 0;
+
+			saslSession->evaluateChallenge(NULL, 0, &initialResp, &initialRespLen);
+
+			string encodedInitialResp(saslContext->encodeB64(initialResp, initialRespLen));
+			delete [] initialResp;
+
+			if (encodedInitialResp.empty())
+				sendRequest(SMTPCommand::AUTH(mech->getName(), "="));
+			else
+				sendRequest(SMTPCommand::AUTH(mech->getName(), encodedInitialResp));
+		}
+		else
+		{
+			sendRequest(SMTPCommand::AUTH(mech->getName()));
+		}
 
 		for (bool cont = true ; cont ; )
 		{
diff --git a/src/vmime/security/sasl/SASLMechanism.hpp b/src/vmime/security/sasl/SASLMechanism.hpp
index 5492e48c..8756471f 100644
--- a/src/vmime/security/sasl/SASLMechanism.hpp
+++ b/src/vmime/security/sasl/SASLMechanism.hpp
@@ -58,6 +58,9 @@ public:
 	  * server (challenge), process it and return data to be returned
 	  * in response to the server.
 	  *
+	  * If the challenge is empty (challengeLen == 0), the initial
+	  * response is returned, if this mechanism has one.
+	  *
 	  * @param sess SASL session
 	  * @param challenge challenge sent from the server
 	  * @param challengeLen length of challenge
@@ -84,6 +87,15 @@ public:
 	  */
 	virtual bool isComplete() const = 0;
 
+	/** Determine if this mechanism has an optional initial response.
+	  * If true, caller should call step() with an empty challenge to
+	  * get the initial response.
+	  *
+	  * @return true if this mechanism has an initial response, or
+	  * false otherwise
+	  */
+	virtual bool hasInitialResponse() const = 0;
+
 	/** Encode data according to negotiated SASL mechanism. This
 	  * might mean that data is integrity or privacy protected.
 	  *
diff --git a/src/vmime/security/sasl/SASLSession.hpp b/src/vmime/security/sasl/SASLSession.hpp
index ccf181cb..21ccc420 100644
--- a/src/vmime/security/sasl/SASLSession.hpp
+++ b/src/vmime/security/sasl/SASLSession.hpp
@@ -96,6 +96,9 @@ public:
 	  * server (challenge), process it and return data to be returned
 	  * in response to the server.
 	  *
+	  * If the challenge is empty (challengeLen == 0), the initial
+	  * response is returned, if the mechanism has one.
+	  *
 	  * @param challenge challenge sent from the server
 	  * @param challengeLen length of challenge
 	  * @param response response to send to the server (allocated by
diff --git a/src/vmime/security/sasl/builtinSASLMechanism.cpp b/src/vmime/security/sasl/builtinSASLMechanism.cpp
index e179e715..9e352334 100644
--- a/src/vmime/security/sasl/builtinSASLMechanism.cpp
+++ b/src/vmime/security/sasl/builtinSASLMechanism.cpp
@@ -120,6 +120,13 @@ bool builtinSASLMechanism::isComplete() const
 }
 
 
+bool builtinSASLMechanism::hasInitialResponse() const
+{
+	// It seems GNU SASL does not support initial response
+	return false;
+}
+
+
 void builtinSASLMechanism::encode
 	(shared_ptr <SASLSession> sess, const byte_t* input, const size_t inputLen,
 	 byte_t** output, size_t* outputLen)
diff --git a/src/vmime/security/sasl/builtinSASLMechanism.hpp b/src/vmime/security/sasl/builtinSASLMechanism.hpp
index 09b46f00..6cecd1b9 100644
--- a/src/vmime/security/sasl/builtinSASLMechanism.hpp
+++ b/src/vmime/security/sasl/builtinSASLMechanism.hpp
@@ -61,6 +61,8 @@ public:
 
 	bool isComplete() const;
 
+	bool hasInitialResponse() const;
+
 	void encode(shared_ptr <SASLSession> sess,
 		const byte_t* input, const size_t inputLen,
 		byte_t** output, size_t* outputLen);
diff --git a/tests/net/pop3/POP3CommandTest.cpp b/tests/net/pop3/POP3CommandTest.cpp
index 4733c96b..139e948b 100644
--- a/tests/net/pop3/POP3CommandTest.cpp
+++ b/tests/net/pop3/POP3CommandTest.cpp
@@ -39,6 +39,7 @@ VMIME_TEST_SUITE_BEGIN(POP3CommandTest)
 		VMIME_TEST(testCAPA)
 		VMIME_TEST(testNOOP)
 		VMIME_TEST(testAUTH)
+		VMIME_TEST(testAUTH_InitialResponse)
 		VMIME_TEST(testSTLS)
 		VMIME_TEST(testAPOP)
 		VMIME_TEST(testUSER)
@@ -97,6 +98,14 @@ VMIME_TEST_SUITE_BEGIN(POP3CommandTest)
 		VASSERT_EQ("Text", "AUTH saslmechanism", cmd->getText());
 	}
 
+	void testAUTH_InitialResponse()
+	{
+		vmime::shared_ptr <POP3Command> cmd = POP3Command::AUTH("saslmechanism", "initial-response");
+
+		VASSERT_NOT_NULL("Not null", cmd);
+		VASSERT_EQ("Text", "AUTH saslmechanism initial-response", cmd->getText());
+	}
+
 	void testSTLS()
 	{
 		vmime::shared_ptr <POP3Command> cmd = POP3Command::STLS();
diff --git a/tests/net/smtp/SMTPCommandTest.cpp b/tests/net/smtp/SMTPCommandTest.cpp
index 6d466865..9480948c 100644
--- a/tests/net/smtp/SMTPCommandTest.cpp
+++ b/tests/net/smtp/SMTPCommandTest.cpp
@@ -37,6 +37,7 @@ VMIME_TEST_SUITE_BEGIN(SMTPCommandTest)
 		VMIME_TEST(testHELO)
 		VMIME_TEST(testEHLO)
 		VMIME_TEST(testAUTH)
+		VMIME_TEST(testAUTH_InitialResponse)
 		VMIME_TEST(testSTARTTLS)
 		VMIME_TEST(testMAIL)
 		VMIME_TEST(testMAIL_Encoded)
@@ -95,6 +96,14 @@ VMIME_TEST_SUITE_BEGIN(SMTPCommandTest)
 		VASSERT_EQ("Text", "AUTH saslmechanism", cmd->getText());
 	}
 
+	void testAUTH_InitialResponse()
+	{
+		vmime::shared_ptr <SMTPCommand> cmd = SMTPCommand::AUTH("saslmechanism", "initial-response");
+
+		VASSERT_NOT_NULL("Not null", cmd);
+		VASSERT_EQ("Text", "AUTH saslmechanism initial-response", cmd->getText());
+	}
+
 	void testSTARTTLS()
 	{
 		vmime::shared_ptr <SMTPCommand> cmd = SMTPCommand::STARTTLS();