CentOS
SMTP Error (550): Failed to set sender (Access denied - Invalid HELO name (See RFC2821 4.1.3))
In this article i will show how to fix error in VestaCP: An error occurred! SMTP Error (550): Failed to set sender "xxx.zzz" (Access denied - Invalid HELO name (See RFC2821 4.1.3)). The problem happens when you try to send email from Roundcube webmail. To