Emails for any client will always come from the following IPs:

The DNS that we send from are:
SMTP.Digitalmailer.com
SMTP1.Digitalmailer.com
SMTP2.Digitalmailer.com
SMTP3.Digitalmailer.com

If you are unable to use the DNS names, the IP addresses below are available.

199.233.227.58
199.233.227.59
199.233.227.60
199.233.227.61