Roundcube Email not Sending/Receiving between accounts

For the past few months, the Roundcube accounts on our Homestead Domain cannot send to one another (via: pc web browser google chrome, pc microsoft outlook, iPhone Mail app). We are running Roundcube version 1.3.14 on google chrome (see attached image). All the email accounts are below 80% on their storage allotment. I have no filters setup to block this and there is nothing in the spam folder or trash or any other folders. Perhaps there is some kind of unintended spam blocking going on in the backend (server-side) that I don't have access to? The status page at http://status.homestead.com/ has been in 404 error for a while now and I'm not sure how to contact Homestead about this except for mentioning it in a thread like this. If anyone else is experiencing this, please speak up. Please help me.