I am seeting up the accounst and domains on my new server. As part of the process I run each site through DNSStuff.com to see if there are any issues I need to resolve. All is well excpet I get a warning that is unique to my IP based sites.

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WARNING

Mail server host name in greeting

WARNING: One or more of your mailservers is claiming to be a host other than what it really is (the SMTP greeting should be a 3-digit code, followed by a space or a dash, then the host name). If your mailserver sends out E-mail using this domain in its EHLO or HELO, your E-mail might get blocked by anti-spam software. This is also a technical violation of RFC821 4.3 (and RFC2821 4.3.1). Note that the hostname given in the SMTP greeting should have an A record pointing back to the same server. Note that this one test may use a cached DNS record.

mydomain.com claims to be host host.maindomain.net [but that host is at ###.###.###.111 (may be cached), not ###.###.###.234].
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How do I resolve this issue?

Thanks,
DB