Thank you for sharing those links,
I have checked those links and found that
"The registration email may end up in the person's spam folder and in others it may not arrive at all. There are many reasons why this might be happening:
I belive that there is something that I have to do with the points that are mentioned. Could someone please guide me with it.
If it's only the verification emails that fail to receive the users, you can try changing the wording within the email body to see if it helps. But I won't expect too much of this - it might help on short term but the spam filters of the email providers will learn and you will have the same problem again at some time in future (rather sooner than later). Also, changing anything in the email header seems not promising to me - after all the other notification emails do reach their destination, so it's not a general problem with the email header.
The most promising point is "server is not trusted". There are ways to improve the credibility of your server but it depends on your server config, if you can use them. You mentioned in another thread that you use the PHP mailer plugin to send the emails from your Elgg site via Gmail. In this case you have no change to improve the credibility of your server because the emails are sent via Google and you can't influence the credibility. Instead you would need to use your own mail server on your own server (or webspace). Do you host your site on some webspace? In case you do, you can ask your hoster about ways to improve credibility, e.g. using the SPF framework, domain keys and setting up a valid PTR record.
As per your suggestion I have changed the content of the verification email and now users are receiving the emails and this happened after I deactivated "PHPmailer" plugin. But, I am afraid as this is only a temporary solution.
Have even asked Godaddy support team to resolve the issue and am waiting for their revert.