I use gmail and get this error when using dnsstuff.com -

Malformed greeting or no A records found matching banner text for following servers, and banner is not an address literal. RFC5321 requires one or the other (should not be a CNAME). If this is not set correctly, some mail platforms will reject or delay mail from you, and can cause hard to diagnose issues with deliverability. Mailserver details:

173.194.77.27 | WARNING: The hostname in the SMTP greeting does not match the reverse DNS (PTR) record for your mail server. This probably won't cause any harm, but may be a technical violation of RFC5321
74.125.45.26 | WARNING: The hostname in the SMTP greeting does not match the reverse DNS (PTR) record for your mail server. This probably won't cause any harm, but may be a technical violation of RFC5321
173.194.76.26 | WARNING: The hostname in the SMTP greeting does not match the reverse DNS (PTR) record for your mail server. This probably won't cause any harm, but may be a technical violation of RFC5321
74.125.45.26 | WARNING: The hostname in the SMTP greeting does not match the reverse DNS (PTR) record for your mail server. This probably won't cause any harm, but may be a technical violation of RFC5321
173.194.76.26 | WARNING: The hostname in the SMTP greeting does not match the reverse DNS (PTR) record for your mail server. This probably won't cause any harm, but may be a technical violation of RFC5321

Is there a way to fix this, or is it fine?