You might be thinking this is a strange piece of news in an era of cloud storage and being able to easily share documents of any size through email.
In fact, last year Microsoft talked about the evolution of email and one of the elements they discussed was to share links to shared files on OneDrive instead of mailing large attachments to multiple people.
When you add the increased collaboration features that are now available through Office Online sharing files from cloud storage makes a lot of sense.
However, there will likely be times when cloud storage is not accessible or you will be offline at the time you need access to that large file so sometimes the old-school way of emailing these attachments is necessary.
Prior to this change the maximum email size allowed on Office 365 was 25 MB but now Office 365 global administrators can change that limit to a maximum of 150 MB for their users in the Exchange Admin Center.
In reality the option can be set anywhere in the 1 to 150 MB range which gives you very granular control over email maximum sizes. This change is also opt-in which means whatever you currently have set for maximum email size will remain in place for users until you choose to change it.
