Doug is correct that this is a looming issue:
Linking to cloud-based office files within the organization is different – those files are within the “possession, custody and control” of the responding party. However, just as linked web sources may be changed or deleted at some point, the same holds true for linked office files. Unlike attachments, which are a snapshot of the file at the time of that correspondence, linked files are evergreen: they can continue to be edited or even deleted, so the evidence as it existed at the time of the email may be lost.
Where I will disagree with Doug though is when he says few people are talking about this. I have this conversation with clients, peers, and others, every single day, sometimes multiple times in a day.
Everyone is talking about it, but they aren’t talking about it in regards to email, rather it is within collaboration platforms like Teams and Slack where shared files are always links, and those links may be in a variety of locations.
Those linked files matter, but not in the same way an email attachment used it, and legal teams are going to have to understand all of that. Is your team ready?