This may tell "Why my mail goes to Bulk folder at yahoo". But I need help.

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?

 

As far as I know this is not the only problem of your mail going into the Yahoo's bulk folder (same with Hotmail).
You will need to ask the webmasters of Yahoo (and Hotmail) to 'white list' your domain also.

Good luck..