If webmail products like Gmail can give millions of users up to 10GB of space each, why should other companies enforce mail quotas and archive data? Like most things, it’s a compromise. In this case a trade-off between cost, usability, and legal requirements.
Internet companies such as Google and Microsoft money to spend on attracting users to their platforms via free software & services, whereas for other commercial enterprises, it’s usually not the core business, and therefore it’s a cost.
Companies recognise the importance of email, internally and externally, and therefore they provide it. At the same time, they want to keep the cost of providing it down, and reducing server load via archiving old, unused data to low-cost storage is a useful way to do that.
Documents build up rapidly in mail files. Organising those documents in some way (e.g. filing into folders) can only get you so far before the sheer volume of data in the mail file starts affecting performance, both user and server. For example, if a user has 10,000 emails in their mail file, the server has to update the database indexes, perform it’s usual maintenance tasks, and back it up. Navigation for the user is slower, as is replicating the data locally, providing access via different mediums, and searching: so reducing the amount of active data in the mail file improves performance, for both the user and server.
As part of providing email to their employees, companies almost always have to comply with legal regulations enforcing the retention of that email for a certain length of time. The best way to do that is to archive it in the original format, so they can always be sure they can meet any legal challenges that might eventuate, as well as for their own needs, records & knowledge management in the future.
These are the main reasons companies should archive email. Of course, there are more, e.g. de-duplication of data. What are the main drivers for archiving in your organisation?