Isoqlog is an MTA log analysis program written in C. It is designed to scan qmail, Postfix, Sendmail, and Exim logfiles and produce usage statistics in HTML for viewing through a browser. It produces a "top domains" statistic according to sender, receiver, total mails, and bytes, and keeps the main domain mail statistics with regard to day's top domain, and top users values for per day, per month, and per year.
The Moxy Mail Proxy acts as a mail server for multiple domains, transparently proxying mail to different hosts and/or ports. Mail servers transparently receive mail on non-standard ports (i.e., other than 25), users retain complete control over their mail server, mail bandwidth usage is logged on a per destination or per email address basis, mail can be directed to multiple servers/ports simultaneously, and more.
mysqmail-qmail-logger is a very small daemon that logs SMTP traffic such as successful delivery and relaying to an SQL database. It splits the information by domain and by users in both the to and from fields, which makes it very easy to count all the SMTP traffic for a given domain name.
mysqmail-postfix-logger is a (very small) daemon that logs all SMTP traffic to an SQL database. It splits the information by domain and user for the From and To fields, making it very easy to count all the SMTP traffic for a given domain name. DTC (Domain Technologie Control) uses it for logging the SMTP traffic.