Consider defining a bean of type 'org.springframework.mail.javamail.JavaMailSender' in your configuration. code example

Example: Field emailSender in com.optum.link.security.importer.utils.SendMail required a bean of type 'org.springframework.mail.javamail.JavaMailSender' that could not be found.

In My project i was reading email properties file like hostname, port etc from spring config server (Spring cloud). 
I was missing a dependency at client end. Once i added that Dependency.

<dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-config</artifactId>
</dependency>

JavamailSender class able to read those properties and worked fine.
In spring boot we need not define JavaMailSender bean manually. spring boot does itself.