Connecting through TLS (for SMTP) is supported in the recent versions, including 188.8.131.523. You can put 587 into the field and connect successfully (for example, in case you're using Office365).
What's not working is keeping your custom value in the filed. When you open your 'Getting Started Wizard' next time, you'll see there 465, though you were connected through 587.
So, this is UI issue and doesn't prevent you from using TLS connection.
Thanks for clarifying.