Linux Server Sendmail SMTP - Invalid HELO

I'm currently using PHP Mail function to send out emails.

However, some emails sent out are not being received by recipents.

Mail Queueing System from DirectAdmin says the following:

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1OTmDh-0007qa-KF-D

This message was created automatically by mail delivery software.

A message that you sent could not be delivered to one or more of its

recipients. This is a permanent error. The following address(es) failed:

tom{at}[url removed, login to view]

SMTP error from remote mail server after MAIL FROM:<admin{at}[url removed, login to view] > SIZE=1836:

host [url removed, login to view] [[url removed, login to view]]: 550 Access denied - Invalid HELO name (See RFC2821 4.1.1.1)

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This needs to be fixed. I suspect something wrong with hostname configuration.

Urgent Job, Budget $30.

Linux Script Install Shell Script System Admin Web Security

Project ID: #726142

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