I am experiencing an error when trying to send mail to certain hosts from my VPS. Here is an example:
SMTP error from remote mail server after MAIL FROM:<firstname.lastname@example.org> SIZE=1409: host recipienthost.com [18.104.22.168]: 550 Access denied - Invalid HELO name (See RFC2821 22.214.171.124)
I am using exim4 and sendmail. At first I thought it was my host name, so I changed that from a numerical value to my website address.
Does anyone know what's wrong and what I need to do?