It seems some other plugin is misconfigured. Try to deactivate them one by one and reload the WP Mail SMTP admin area page after each deactivation.
I’m sorry. My site is live and I have over 20 plugins to deactivate them. Thank you tho. I’ll try something else and see.
I have the same issue, on several websites, and across different servers.
I suspect there is some code issue, because this happens even when there are no other plugins active.
I tested after the update to version 0.10.1 and observed that the test is successful, and test email received. Thank you.
Interestingly… If I install this on a new site (that has not had this plugin before), sending and tests all fail. 🙁
Sorry… My bad. The version was 0.10.1 (not 0.11.1) – So… YES it’s fixed and working! 😉