Cannot use PHP mail to send email


I'm trying to use PHP mail function to send the email in my website. But I found that they cannot be sent. Here is the status in Postfix Mail Queue:

host[] refused to talk to me: (mxgmxus004) Nemesis ESMTP Service not available 554-No SMTP service 554 invalid DNS PTR resource record, IP=


Howdy -- it sounds like the recipient's server is rejecting the email due to a missing reverse DNS (PTR) record.

It may be as simple as adding one of those.

To add a reverse DNS record, you would need to contact the provider for your server, and ask them to add it for your IP address.