CWP6 Mail SMTP Error!

[SpeedTroller]

Hello dear forum members,

CWP gives error when sending mail from the roundcube mail system from the panel. You can see the error below. I'm waiting for your help.

SMTP problem (450): "uxxxxxxx@gmail.com" could not Add recipient (4.7.1 <localhost>: Helo command restricted: host not found)

Ss: https://i.hizliresim.com/2azr1d.png