Microsoft Exchange does not natively support ATRN.
There is an ATRN utility that you can download from the following URL:
Example parameter would be:
xatrn -v -a 366 -p 366 -s domain.com mail.dns2go.com domain.com pwd domain.com
Replace "domain.com" with your domain name and "pwd" with the password to dequeue email.
In Exchange the Default SMTP Virtual Server will need to be edited to listen on port 366. Without this configuration mail will not be able to be downloaded from the DNS2Go MailServers.