This setup works for our customer who is using office365.com, I hope it will help you:
1) In hMailServer, In Settings --> Protocol --> SMTP --> Delivery of e-mail tab --> SMTP Relayer
Remote host name: smtp.office365.com
Check "Server requires authentification" and enter username and password
Connection Security: STARTTLS (Optional)
2) In Settings --> Advanced --> IP Ranges add an IP address of the ICP 3300 (in Lower IP and Upper IP)
Check "Allow connection SMTP", uncheck POP3 and IMAP
Check the required options under "Allow deliveries from" (I have all unchecked but be aware that it can be abused by spammers)
Uncheck the options under "Require SMTP authentication" (the ICP 3300 will not provide SMTP user and password)
3) Also make sure hMailServer service is under exceptions in the windows firewall
4) In ICP 3300, under System Options enter the IP address of the hMailServer PC to the "Email Server" field, also specify the sender's e-mail address in "Email - Sender's Address"
5) In hMailServer use Status --> Logging watch the SMTP activity