yes thanks, postfix works fine with SendGrid API key, issue is only with roundcubemail Web interface so suspect that config.inc.php (still using user/pass) needs to be updated to start using the API
I tried but still got the same 535 Error, so was wondering if there is any Roundcube documentation so I make sure API are entered correctly?
Respective communication from SendGrid below:
Secure Your SendGrid Account With API Keys and Two-Factor Authentication (2FA) Twilio SendGrid will soon begin enforcing API Key authentication for all API requests and SMTP configuration, as well as requiring Two-Factor Authentication upon login. We have begun reaching out to customers to upgrade to API Keys where applicable, and to enable 2FA on their SendGrid accounts using SMS or Authy.