Email notification cannot be sent due to error: 'javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?' (4295919)

Email notification cannot be sent due to error: 'javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?'

Possible error messages:
WARN    [Action-4-thread-69] com.quest.nitro.service.action.ActionService - Failed to invoke action EmailAction with parameters {foglight_rule_name=xxx, foglight_severity_level_name=xxx, foglight_rule_id=xxx}
com.quest.nitro.service.action.api.ActionInvocationException: Failed to send email to recipients=xxx, cc=null, bcc=null [org.springframework.mail.MailSendException: Mail server connection failed; nested exception is javax.mail.MessagingException: Exception reading response;
  nested exception is:
    javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?]
    at com.quest.nitro.service.action.impl.email.EmailAction.invoke(EmailAction.java:152)
...
Caused by: org.springframework.mail.MailSendException: Mail server connection failed; nested exception is javax.mail.MessagingException: Exception reading response;
...
Caused by: javax.mail.MessagingException: Exception reading response;
...
Caused by: javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?


ERROR   [EventPublisher-0] com.quest.nitro.service.event.EventService - An exception thrown by subscriber: com.quest.nitro.service.notification.channel.AlarmNotificationManager@591d6b4f while processing ant event: DataObject of type 'foglight-5:AlarmSystemEvent' for datasource: 'foglight-5:foglight-5':/anonymous/0bdc301c-d4fd-4338-8c13-5d133690d790
org.springframework.mail.MailSendException: Mail server connection failed; nested exception is javax.mail.MessagingException: Could not connect to SMTP host: smtp-host, port: 587;
  nested exception is:
    javax.net.ssl.SSLException: Unsupported or unrecognized SSL message. Failed messages: javax.mail.MessagingException: Could not connect to SMTP host: smtp-host, port: 587;
  nested exception is:
    javax.net.ssl.SSLException: Unsupported or unrecognized SSL message; message exception details (1) are:
Failed message 1:
javax.mail.MessagingException: Could not connect to SMTP host: smtp-host, port: 587;
  nested exception is:
    javax.net.ssl.SSLException: Unsupported or unrecognized SSL message
...
Caused by: javax.net.ssl.SSLException: Unsupported or unrecognized SSL message

1. Navigate to Administration | Administration | Email Configuration.
2. Set the Enable SSL? option to False.
3. Set the Enable STARTTLS? option to True if supported by the mail server.
4. Save the email configuration.