With such a tool, you can view numbers of e-mails sent through your mail server, stopped e-mails by different filters (RBL, content filters, MIAS, ...), stopped by anti-virus, ....
You can also perform different statistics in a simple and fast way. Is has the possibility to extract all accounts (with passwords) from a given domain, search within Merak Logs and you can even watch the log session for a specific e-mail.
Finally, it can show you key data for every user / domain: last received /sent e-mail date, last pop3 connection, inbox size, total mailbox size and number of e-mails.

For more information, screenshots and trial version, see http://www.arianesoft.com/products/log-analyzer