Daily report is not working with SMTPS

When using the parameters below in grouper.properties:

mail.smtp.server = xxxx.yyyy.zzzz
mail.smtp.user = xxx/yyy
mail.smtp.pass = yyyy
mail.smtp.ssl = true
mail.smtp.port = 587
mail.from.address = xxx@yyy.zzz

.we get the following error:

javax.net.ssl.SSLException: Unrecognized SSL message, plaintext connection?

Just out of curiosity, when we turned TLS off :

mail.smtp.ssl = false

now we get the following error:

javax.mail.MessagingException: Could not connect to SMTP host: xxxx.yyyy.zzzz, port: 25, response: 421