What is SPF records and How to setup?

Why Is My Emails Getting As Spam?
Check above things.

First we need to check Email Headers.
1. Return Path
2. To
3. From
4. We should not use CAPS because not only being unprofessional, but it
also triggers spam filters. To land in the Spam folder consistently,
please do not USE ALL CAPS IN THE SUBJECT LINE AND THE BODY FROM TO and
Excessive punctuation (e.g. -/, ;^%#$@+ * "').

E.g. as follows.

1. Email "From : ADMIN ENROLL <noreply@exmaple.com>" getting
spam in gmail.com sometimes and if we not change it will increasing
count.

2. Email "From: noreply@exmaple.com" it
getting in mailbox, check the CAPS deference.

http://php.net/manual/en/function.mail.php
http://www.niso.org/khelp/kmlm/user_help/html/examine_mail_headers.html

Please check this too. It can be understand better. :)
http://www.infusionblog.com/email-marketing/7-ways-for-your-email-to-land-in-the-spam-folder/

Check SPF for Domain.:
http://www.microsoft.com/mscorp/safety/content/technologies/senderid/wizard/

What is SPF records and How to setup?
http://www.kazeli.com/help/index.cfm?pageloc=quest&questid=435&catid=337,338

To diagnose the mail. Why its going in Spam.
Check tool:
http://mxtoolbox.com/
Here you can check following points
1. Mxlookup : For your domain and ip
2. Blacklist : For your IP
3. Diagnostics : SMTP Diagnostics, check your mail server
4. Analyze Headers : Check your mail headers.
5. SPF Records : Check your Sender Policy Framework
7. DNS Lookup : Check your Domain lookup.

If you check above all things your mail will not go in Spam.!