Users on Open Xchange platform will not be able upload inline images higher than the following resolution:
12087962 px (~ 4064 x 2704 (11.1 megapixels) + 10%) or Images greater than 5 MB.
Error : Upload file is invalid or illegal.
As of now, we will not be increasing this limit. However, sysads can consider increasing this limit in case of multiple connects. Please route such requests via Product Managers.
Reference JIRA : https://jira.endurance.com/browse/TUW-3790