email with Verification Link not being received by new users

[Get Sociable]

We've created two new account in Jira Software however they have not received the email with the verification link. I resent it multiple times and even deleted the accounts and set them up again. I am able to assign them to stories in Jira and they are getting the notification emails when changes are made to the stories unfortunately however when they try and open the issue it’s telling them to check the mailbox to set up their account. However again no email is received and they cannot log into Jira Software.