If you have problems delivering mail to Office 365 users trough SecureMail
Make a Powershell script that can be run to allow all of the IP's that our O365 customers would need to allow. This creates a mail rule in the Exchange Admin Center
# Use this script to create an inbound rule for
# 365 W.15 customers using Norman SecureMail.
# more info here: http://technet.microsoft.com/en-us/library/jj919237%28v=exchg.150%29.aspx
New-TransportRule -Name "Norman SecureMail" -priority 0 -comment "This rule must remain in place to allow Norman SecureMail to bypass EOP filtering." -SenderIPRanges 126.96.36.199/25,188.8.131.52,184.108.40.206,220.127.116.11,18.104.22.168,22.214.171.124,126.96.36.199,188.8.131.52,184.108.40.206 -setscl -1