We have 2 exchange servers (2003) with over 2000 mailboxes on each. I am 99% sure a significant percentage of these mailboxes arent used, but I need a way to prove this. Some of these are group mailboxes and users are given delegate rights. Please advise any techniques you know of to identify stale unusued mailboxes, I did think about traffic coming in/out Finally, can you think of any risk as to keeping stale/unusued mailboxes open? What is the overall risk or importance in deleting them/archiving them once they are no longer required? I am trying to build a case why we need to get rid of them, whats the point, whats the risk etc.

Message tracking will probably show mostly SPAM going to those mailboxes if they aren't being used, but that's a good place to start. You could always simply send a message to those mailboxes asking if anyone is actually reading or accessing messages in it. If you get no response, that's a good indication as well. The risk? Well those mailboxes will eventually reach their send/receive limits and start bouncing mail back to senders and external spoofed senders that could land your org on some blocklists. Not to mention the increased usage of disk space and larger backups.

Message tracking will probably show mostly SPAM going to those mailboxes if they aren't being used, but that's a good place to start. You could always simply send a message to those mailboxes asking if anyone is actually reading or accessing messages in it. If you get no response, that's a good indication as well. The risk? Well those mailboxes will eventually reach their send/receive limits and start bouncing mail back to senders and external spoofed senders that could land your org on some blocklists. Not to mention the increased usage of disk space and larger backups. WHats the risk with larger backups, not being a backup admin myself? And as to maiolbox full responses, does that really lead to you being added to blacklists? i.e. the whole company would be added?

Message tracking will probably show mostly SPAM going to those mailboxes if they aren't being used, but that's a good place to start. You could always simply send a message to those mailboxes asking if anyone is actually reading or accessing messages in it. If you get no response, that's a good indication as well. The risk? Well those mailboxes will eventually reach their send/receive limits and start bouncing mail back to senders and external spoofed senders that could land your org on some blocklists. Not to mention the increased usage of disk space and larger backups. WHats the risk with larger backups, not being a backup admin myself? And as to maiolbox full responses, does that really lead to you being added to blacklists? i.e. the whole company would be added? No real risk with larger mailboxes per se, just pointing out that they take more space and require larger backups, something to consider. Do full mailbox NDRs lead to getting blocked? Not typically, but if you generating a bunch and consistently, some gungho RBL or email administrator may just decide that he wont accept anything from your sending ip address until it stops.