This configuration setting expects the SMTP server to offer SMTP over SSL (SMTPS) but Office365 offers SSMTP (SMTP on submission port 587/tcp with optional connection upgrade with STARTTLS).
See also:
Yes. They are the credentials for the SMTP service. Without those, the SMTP service won’t allow you to send emails.
No, HTTPS and SMTP/SSMTP/SMTPS have nothing to do with each other.
