I am using Zoho mail to send and receive emails with my own domain. Whenever a mail is sent to a Gmail for example, a question mark with following message is displayed "Gmail couldn't verify that lookapp.lk actually sent this message (and not a spammer)". I understand that I need to add SPF TXT record in my domain manager in order to avoid spam filters. So I did what is explained in here but still the problem remains. 

My domain is lookapp.lk

Any help is greatly appreciated!