Our company is doing business with many sales platforms, like eBay, Amazon, Cdiscount, Real, etc.
For eBay and Amazon we are using the ChannelReply plugin for handling the customer messages on the platforms, but we would like to have a message API integration in Zendesk for a lot of other sales platforms as well. I've asked ChannelReply for their roadmap but none of our 50+ platforms are present here, nor they want to integrate any platform from our list as a customization project.
With our previous CRM tool, we built a "middleman server" that was in charge of processing the messages between the salesplatform and the CRM tool (Middleman server grab new the message from the platform, create a ticket in CRM, the agent reply is sent back to the middle man server who send the reply back to the platform via API).
Zendesk Sunshine isn't an option because they support only the social media and "chat" apps.
I can imagine that a lot of other companies have to deal in the same way (other than let the agents working direct on the platforms to reply to customer messages, which is not good for productivity reporting, scheduling, etc.). How are other companies dealing with messaging API's for offline messages (in the form of an "email").