Retry SMTP connection if no authentication is supported

[mcoles]

Several users have had issues or have been confused by their SMTP servers rejecting attempts to send email, based on the fact that they provided auth information (username/password). We could change the behavior so that, when VizAlerts initiates, it tests for the SMTP server connection. It would first attempt to authenticate, if the admin entered username/password info in the config file. If the auth attempt was rejected outright because the SMTP server uses no authentication at all, then retry without it.

There may be a way to simply specify this in the library call itself, rather than adding code on our end. It will at least make things a bit easier on the config side.

See https://community.tableau.com/message/554475