We have developed an application to extract data from Yammer using the Yammer APIs. We're authenticating using the verified admin's credentials. According to the data export CSV file we know that there are some 25K messages in the network, but we only get 10K messages via the API. Initially thought that the difference was private messages, but the missing messages are a mix of private and public messages.
The API call we are using is: https://www.yammer.com/api/v1/messages.json . We are using the 'older_than' parameter to scan through all the messages.
In the end we had to query the missing messages individually but that is not a very efficient process.
Any ideas about what we could be doing wrong, or why the APIs are missing to many messages?