====== SpringBoot Email ======
  * [[https://www.baeldung.com/spring-email|Guide to Spring Email | Baeldung]]
  * ''spring-boot-starter-mail''를 사용해 자동 설정 가능
  * [[https://docs.spring.io/spring-boot/docs/current/reference/html/boot-features-email.html|37. Sending Email]]
  * [[https://github.com/spring-projects/spring-boot/blob/v2.1.0.RELEASE/spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/mail/MailProperties.java|MailProperties]] 로 설정