Weird Error when Connecting Spring’s JavaMailSender to Postfix

I had a weird error today when trying to connect to my server’s postfix mail server. It’s weird because i never had this kind of error when connecting to Google Mail server. This is the error that i see on postfix’s log.

Mar 26 01:50:19 localhost postfix/smtpd[24907]: connect from localhost[127.0.0.1]
Mar 26 01:50:19 localhost postfix/smtpd[24907]: setting up TLS connection from localhost[127.0.0.1]
Mar 26 01:50:19 localhost postfix/smtpd[24907]: SSL_accept error from localhost[127.0.0.1]: 0
Mar 26 01:50:19 localhost postfix/smtpd[24907]: warning: TLS library problem: 24907:error:14094416:SSL routines:SSL3_READ_BYTES:sslv3 alert certificate unknown:s3_pkt.c:1193:SSL alert number 46:
Mar 26 01:50:19 localhost postfix/smtpd[24907]: lost connection after STARTTLS from localhost[127.0.0.1]
Mar 26 01:50:19 localhost postfix/smtpd[24907]: disconnect from localhost[127.0.0.1]

This is my email configuration on Spring’s applicationContext.xml.

<bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
	<property name="host" value="localhost"/>
	<property name="port" value="25"/>
	<property name="username" value="admin@whatever.com"></property>
	<property name="password" value="password"></property>
	<property name="javaMailProperties">
		<props>
			<prop key="mail.smtp.auth">true</prop>
			<prop key="mail.smtp.starttls.enable">true</prop>
		</props>
	</property>
</bean>

After googling for a while, i found out that somehow the error happen because of TLS problem. The workaround is actually easy, i disabled the starttls property on bean mailSender.

<bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
	<property name="host" value="localhost"/>
	<property name="port" value="25"/>
	<property name="username" value="admin@whatever.com"></property>
	<property name="password" value="password"></property>
	<property name="javaMailProperties">
		<props>
			<prop key="mail.smtp.auth">true</prop>
			<prop key="mail.smtp.starttls.enable">false</prop>
		</props>
	</property>
</bean>