What is Sender Policy Framework (SPF)
Sender Policy Framework (SPF) is an email authentication method which ensures the sending mail server is authorized to originate mail from the email sender's domain.This authentication only applies to the email sender listed in the "envelope from" field during the initial SMTP connection. If the email is bounced, a message is sent to this address, and for downstream transmission it typically appears in the "Return-Path" header. To authenticate the email address which is actually visible to recipients on the "From:" line, other technologies such as DMARC must be used. Forgery of this address is known as email spoofing, and is often used in phishing and email spam.
The list of authorized sending hosts and IP addresses for a domain is published in the DNS records for that domain. Sender Policy Framework is defined in RFC 7208 dated April 2014 as a "proposed standard".
Ok after a serious explanation from Wikipedia here is a short explanation and what to do:
For security reasons, email administrators try to block incoming mail that is not set up appropriately,so they check if sender and coming mail is matched. To check those mails they use the SPF RECORD which should be done by you.
To avoid of this kind of risks you should add or fix your spf record for your domain like this (i.e we used our domain name you should be using your own domain name):
v=spf1 a:subdomain.eska.biz a:eska.biz ip4:xxx.xxx.xxx.xx include:_spf.google.com ~all
The example spf record is checking cname, IP and also service providers details.
Ref : Wikipedia