How can I check if shared mailboxes are actively redirecting emails?

From what you've described, these shared mailboxes might just be acting as distribution lists if they're only redirecting. If they're meant to keep a copy of the emails too, that's a different story. You could create aliases, but that could complicate things since the emails would show as coming from the individual instead of the shared mailbox. It’s something to consider.

I can’t help but wonder why you want to remove them if everything appears to be functioning correctly and the shared mailboxes don't incur any costs? There's a principle called Chesterton's Fence—sometimes you need to understand the reason behind something before making changes. If they are primarily used for redirection, you may want to explore distribution lists or aliases as more efficient solutions, but there may be other factors at play that you haven't considered yet.

Why not send an email to these shared mailboxes and see if there’s any reply? This would help determine if there’s any traffic going through those boxes. But be aware, it's not just about whether the redirect rule is working; you want to confirm that there’s actual email being sent to the shared boxes to begin with. Good luck with finding the evidence you need!

Honestly, this seems more like a management issue. Having 1,000 shared mailboxes is quite excessive unless you have a dedicated email admin. You might want to get buy-in from the higher-ups so they can help you tackle this and make it more manageable. You could pitch it as a matter of efficiency—fewer mailboxes could mean quicker email delivery. If they truly need multiple addresses redirecting to one person, consider using aliases or distribution lists instead of shared mailboxes, which shouldn't automatically forward mail around like that.

If you really want to see if the boxes are being used, you could just block the emails temporarily and see who complains about it. That might give you a clearer picture of what’s essential.