Dear Mel,

There can be several reasons forbidding you deleting mailbox.
Please be more specific, what exactly is the issue.
Steps to delete the mailbox are similar as deleting any other records - you open it and choose record -> delete

What's the issue?

Mailbox can be opened trough module E-mail and conferences -> Registers -> Mailboxes -> marking the mailbox -> pressing the "Properties" button.

Alternate route in newer versions could be module Technics -> Settings -> Mailboxes.

In older versions you might have to enable for a while the e-mail and conferences module in the System -> Settings -> Configurations -> CRM flip

Other issue could be that the mailbox has mails in it - you first have to delete those. You can do it either manually or use E-mail and conference module maintenance function "Empty Mailbox".

Let me know did this help or please be more precise in describing the issue!

Best regards,
Eberstein Business Solutions.