why when i send an email, always go to bulk(spam) not to inbox..?

anyone of you can help me, what the correct coding to send email to go inbox for example to verify an email ?

Hi,
Do the following

1. mark the domain in question as not spam in yahoo
2. if running server from home network, do a whois.sc and see if your isp is listed in spam.

yes...always i sent an email go to spam (bulk)..
why..?

i'm not understand very well....please help me ..

thanks...