harbor: Unable to send emails using Office 356 smtp server

Expected behavior and actual behavior: Unable to send emails using Office 356 smtp server with STARTTLS encryption.

Steps to reproduce the problem:

• Email Server: smtp.office365.com
• Email Server Port: 587
• Email Username: username
• Email Password: password
• Email From: admin <noreply@domain.com>
• Email SSL: True
• Verify Certificate: True

Reference: https://support.microsoft.com/en-us/office/pop-imap-and-stmp-settings-8361e398-8af4-4e97-b147-6c6c4ac95353

Versions:

• harbor version: v2.2.0-ec0ba116
• docker engine version: -
• docker-compose version: -

Additional context:

• Log Files

2021-03-19T21:19:19Z [ERROR] [/core/api/email.go:113]: failed to ping email server: tls: first record does not look like a TLS handshake
2021-03-19T21:19:21Z [ERROR] [/core/api/email.go:113]: failed to ping email server: tls: first record does not look like a TLS handshake
2021-03-19T21:22:34Z [ERROR] [/core/api/email.go:113]: failed to ping email server: tls: first record does not look like a TLS handshake

#5757