Can't set up notification emails on AIO 30 - A problem occurred while sending the email

I can’t send notification emails, no matter what smtp server I try - even my ISP’s, which requires no authentication, I always get :

A problem occurred while sending the email. Please revise your settings. (Error: Email could not be sent. Check your mail server log)

I tried putting the workaround,

‘mail_smtpstreamoptions’ =>
array (
‘ssl’ =>
array (
‘allow_self_signed’ => true,
‘verify_peer’ => false,
‘verify_peer_name’ => false,
),
),

in my config.php, but no luck.

Is this a bug?

Deirdre