where can i find SSL on iPhone setting

Go to Settings>Passwords & Accounts. Then select the account in question. On the next screen, tap the account, then go to Advanced. You should see it there for the incoming mail. Go back to where you found Advanced, and tap on SMTP, that is the outgoing server, tap that, select your accounts outgoing server and check your SSL there too. Buy your email provider should be able to tell you if you need SSL for your mail account. It should configure automatically when you add the account if it is needed.