The Outgoing server (SMTP) %S does not seem to support encrypted passwords. If you just set up the account, try changing the 'Authentication method' in 'Account Settings | Outgoing server (SMTP)' to 'Password, transmitted insecurely'. If it used to work but now doesn't, you may be susceptible to getting your password stolen.
The Outgoing server (SMTP) %S does not seem to support encrypted passwords. If you just set up the account, try changing the ‘Authentication method’ in ‘Account Settings | Outgoing server (SMTP)’ to ‘Password, transmitted insecurely’. If it used to work but now doesn’t, you may be susceptible to getting your password stolen.