Jason Hendriks on "[Plugin: WP Mail SMTP] SMTP mail option stopped working within last week"

GoDaddy?

["Host"]=>
string(24) "smtpout.secureserver.net"

This is not a valid GoDaddy server, AFAIK. Where the heck did you get it? Did you mean relay-hosting.secureserver.net?

That said, if I switch to the PHP mail function, it resumes working.

That's because PHP Mail uses SMTP to localhost on port 25, which IS a valid mail server at GoDaddy.