SMTP greeting
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:
74.201.154.201 | 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
165.254.168.50 | 250-mx.zohomail.com Hello dnsstuff.com (adf-b.dnsstuff.com (74.115.12.14))250-STARTTLS250 SIZE 53477376
Because the other server 165.254.168.50 doesn't show this warning.