Quick note of interest:
Be aware that when an Office365 distribution group is created, it will by default deny email from users outside the Exchange Online organization. I tried to send an email to our info address:
Exchange 2013 distribution groups are not sender-restricted by default, so this took me by surprise. I’m glad I tested delivery before, for instance, publishing the address on a traffic-driving website.
To solve the issue, navigate to your Office365 Exchange Administration Center and either
- enable senders inside and outside your organization, or
- restrict allowed senders to a specific list of addresses (external and internal).