Hi @Tonito Dux ,
When it comes to large attachments, agree with what you have mentioned, saving files to a cloud service like onedrive and then sharing a link would be the best practice, see :
Send large files with Outlook
As regards to your concern about tracking the contents of the files inside the message when journaling, I am assuming that you can look at the permission stuff of the cloud storage. For instance, as far as I know, a SharePoint document library can be set to not allow users to delete files, so you can create a particular document library for users to upload the large attachments for sharing, and meantime prevent them from deleting any files by setting the permissions.
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