Episerver Reach is completely ESP-agnostic and can be used in email templates sent by any Email Service Provider.
In the HTML and preview tab we have added a list of popular ESPs, but this list is not exhaustive and is updated on a regular basis.
If you don't see your Email Service Provider in the drop-down, then you can select "Custom" and enter the correct email address variable manually. If you're unsure what the correct variable is, please contact your Email Service Provider.