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Developers that wish to use the MailUp REST API must first request a developer account 
get a pair of API keys*
Once logged into their MailUp developer account, they can use the Developers tab to request application credentials (client_id and client_secret). Without these credentials the application will not be recognized by the authorization server and it won't be able to access the system. We recommend that these credentials are saved in a safe way (e.g. inside the application's non-public source code) in order to prevent any changes. The developer is responsible for keeping them secret and safe.
Please *Please contact MailUp support if the MailUp Dev portal is not accessible.
Authorization
The client application requests to be authorized to communicate with the MailUp REST API by sending its private credentials to the authorization server.
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