[email issue] how to set domainkeys

[aminulsumon]

here is a portion of header from my yahoo mail

correct one header(non bluehost server):
Authentication-Results: mta144.mail.ac4.yahoo.com from=shopno-dinga.com; domainkeys=neutral (no sig); from=shopno-dinga.com; dkim=neutral (no sig)

incorrect header(bluehost server):
Authentication-Results: mta179.mail.ac4.yahoo.com from=shopno-dinga.com; domainkeys=pass (ok); from=shopno-dinga.com; dkim=neutral (no sig)

this is the only difference between yahoo spam mail and inbox mail. so what i need is to change, domainkeys OR my question is :
how to set domainkeys for bluehost server.

[cade]

That header is saying that the domain key included for the message sent by Bluehost is valid (pass) and the message sent from the non-Bluehost server isn't using domain keys. Unless Yahoo is suddenly penalizing for the use of domain keys (a technology that they primarily developed as a means to ensure that messages actually originate at an authorized sending domain), I would say that the domain key probably isn't the issue that is causing the message to end up in the SPAM box.