I have set up ISPconfig and went to DNSreport.com, they said that 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. mail.mydomain2.com claims to be host server1.mydomain1.com [but that host is at 203.78.a.b (may be cached), not 203.78.a.c]. * I now use ISPconfig 2.1 I have added SPF Record alread as following: mydomain2.com. IN TXT "v=spf1 a mx mx:server1.mydomain1.com mx:mail.mydomain2.com ip4:203.78.a.b ip4:203.78.a.c ~all" But SPF does not help. I still get warning at DNSreport.com. How can I do to solve this problem?