First, apparently mail.optonline.net doesn’t support the login authentication method. You’ll need to talk with them to find out what type of authentication method they do support, hopefully it is one supported by the Python channel. It could be that your ISP doesn’t want third party services using their email servers. Reliably sending email is very tricky. It gets harder and harder as time goes by, due to spam, and spam countermeasures. You might want to try a specific email service. We use mailgun.com, we’ve been very happy with it and so far it hasn’t cost anything.
Secondly, you just published your optonline.net password on a public web page. I would recommend that you drop everything and change that password immediately. And if you used that password anywhere else, you need to change it every place it has ever been used.