if your inbox service only returns X elements (usually 1000) but there are more. you can increase the page size the service requests from the server.
if you are calling the inbox like
and it states that it returns only 1000 items even though it also states that there are more and in the return the value for size is 1000 that indicates that the pagin is in your way. I'll request paging to be implemented in the inbox but for the time beeing we need to increase the page size.
to achieve that we need to alter the inbox-prod.yml to include these two lines and restart the inbox service:
after that the request should gather more items
BUT: if you increase that number this will eventually have a performance impact. So the much prefered course of action is to question if an inbox with so many items is maybe an indicator of bad design choices.