So first of all create a new app password at your mail server, copy it to the SMTP settings, and then run a test using the plugin's test email function and THEN send the order emails. This way we can isolate the problem... (And before we do this, please double check password to be correct).
Can you do this, please?
A. Generate a new password at your mail provider, copy the password and paste it to your smtp plugin settings
B. Try to send our test email with the plugin
C. Let us know the result