How can I retain emails for 7 years with a 50GB M365 group mailbox?

Exporting your emails as .PST files is another approach. You can back them up to your own systems for long-term retention. Just be aware that this method can be cumbersome if you have a lot of users.

Definitely look into using archive options. Even though there are some limitations on archiving licensed mailboxes, you can use shared mailboxes to help with this. Setting retention policies directly on those archives will ensure you meet compliance without running out of space.

One approach is to keep emails for one year in the main mailbox and then transfer the rest to an archived mailbox, where you can retain them for 6-7 years before deleting. This way, you stay compliant without overwhelming the primary mailbox.

It's a good idea to have both an archive and reliable external backups. Using Microsoft's built-in options can be tricky, so consider third-party solutions that specialize in email retention, just to ensure that nothing important gets lost.

I suggest working closely with your compliance team to choose an archiving solution that meets your company's needs. An immutable archiving solution is essential for compliance retention, as it prevents users from deleting messages.