If you find that emails are not getting through to you, you can add the following IPs / IP address ranges to your email whitelist as these are the IPs that SkyPrep emails originate from:
199.255.192.0/22
199.127.232.0/22
54.240.0.0/18
167.89.94.224/32
168.245.16.5/32
Note: please be aware that these IPs can change, so check back from time to time to keep updated on the current IPs.