Spring Mail

• Spring abstraction over JavaMail API
• Used to send emails via SMTP
  • Not implement SMTP, but use it
• Auto-configured by spring-boot-starter-mail

Spring Boot App
   ↓
JavaMailSender
   ↓
SMTP Server (SendGrid / MailHog)
   ↓
Recipient Mail Server
   ↓
Inbox (Gmail / Outlook)

SMTP (Simple Mail Transfer Protocol)

• A protocol used to send emails (like post office)
• Works at application layer
• Sending email from client → server
• Server → server forwarding

Does NOT:

• Read inbox
• Store emails long-term
• Provide UI

Best practice

• Async Email Sending
  • @EnableAsync on main
  • @Async on mail service method
• Do NOT send mail inside DB transaction
  • If email fails → whole transaction rolls back.