HELO vs EHLO: Why Your SMTP Greeting Can Hurt Email Delivery Your SPF, DKIM, and DMARC records may all look correct while your mail server still introduces itself as: EHLO localhost or: EHLO server1.internal That greeting happens before the message body is transmitted and can become one of the first identity signals a receiving server evaluates. What HELO and EHLO actually do When one mail server connects to another, the receiving server fi...