For Meetio to work on your network there are a few ports that needs to be open in order for the devices to access your calendar and Meetio Admin (the central administration tool):
Meetio Admin:
- Port 443 (TCP) to admin.getmeetio.com
- Port 443 (TCP) to storage.getmeetio.com
- Port 443 (TCP) to stats-api.getmeetio.com
- NTP (Time)
- Port 123 (UDP) to ntp.lth.se and 2.android.pool.ntp.org or your custom NTP server (Meetio devices can also get NTP-server address from the DNS if you have configured it as an SRV-record).
Office 365
- Port 443 (TCP) to outlook.office365.com
- Port 443 (TCP) to graph.microsoft.com (Only if using oAuth)
G Suite
- Port 443 (TCP) to www.googleapis.com
Exchange
- Port 443 (TCP) to your Exchange-server EWS base URL (most likely something like https://mail.domain.tld)