Dear Zerigo Customer, 
  
  Effective April 30, 2017, Zerigo DNS will shut down permanently. We thank you for your  
  business and apologize for this inconvenience. 

  If you are managing a public Web site or other Internet domain using Zerigo DNS, you must
  migrate to an alternative DNS provider prior to April 30th, 2017 in order to prevent a DNS
  error message from displaying when a user visits your website. 

Edit to add: the email looks legitimate at first glance, and unlike the one on the Reddit thread does not come from "Rexx.com". It hasn't fallen into Gmail's spam box either.