550 Please turn on SMTP Authentication in your mail client

[kevin616]

"550 Please turn on SMTP Authentication in your mail client, or login to the IMAP/POP3 server before sending your message. mail-yb1-f180.google.com [209.85.219.180]:58570 is not permitted to relay through this server without authentication."

I've set up an email within my cpanel and am using roundcube as my email client. This is a fresh install and am having issues with recieving emails. I can send emails from my roundcube to an external email successfully. If I try to reply (using the same external gmail email account I sent it to)it fails to send the reply with the above code.

Im extremely new to setting up a server email. Any help would be appreciated.
Thanks in advance

[SKaero]

If you setup Roundcube with the SMTP details check if any of this other issues in cPanel are causing the issue: https://support.cpanel.net/hc/en-us/articles/360058963474-550-Please-turn-on-SMTP-Authentication-in-your-mail-client

[kevin616]

Ill check the link. THANKS!
It seems that I can receive emails from some locations.. but not all, including not from gmail.