How can I use Mailissa with a configured EwsAllowList?

If you have configured an EwsAllowList on your Exchange Server, you will need to add Mailissa to this EwsAllowList. The error message that might occur otherwise is "access to odata is disabled"

EwsAllowLists can be configured on an user-basis or global

First of all you will need to connect to the Exchange Server. In a M365 Environment you can achieve this for example by connecting via Powershell (Connect to Exchange Online via Powershell)
Once connected, you need to add at least the value mailissa/core to the EwsAllowList. For example you can execute the following command to add all values starting with mailissa/ to the global EwsAllowList
  1. Set-OrganizationConfig -EwsApplicationAccessPolicy EnforceAllowList -EwsAllowList @{Add='mailissa/*'}

The method to connect and the commands that need to be executed might differ for different Exchange Server types (On Premise, Online, Hybrid)