Measuring Mail Server Utilisation

For the sake of simplicity, it is assumed that all servers in the system are equally powerful. If this is not the case then weightings can be used, such that servers are allocated a load proportional to their power. Periodically a script can be run over the sendmail and cucipop logs to generate statistics. The following factors may be taken into account and weighted according to their resource consumption.

• Number of message delivered via SMTP, as per sendmail logs. This is intended to take into account the system resource required to accept an SMTP message, regardless of its size. This resource includes accepting a connection from a remote host and anti-spam and anti-relaying checks that the MTA runs through for each message.

• Size of incoming SMTP mail, as per sendmail logs. This takes into account the additional system resources required to handle larger messages.

• Number of POP3 requests, as per cucipop logs. This takes into account the resource required to handle a POP3 request, regardless of the amount of data transfered and the size of the mailbox accessed. In particular, this takes into account overhead in authenticating a user.

• Mailbox size, as per cucipop logs. This takes into account the resource required to scan through a user's mailbox. This is particularly costly under some POP3 daemons, including cucipop.

This does not take into account the data transfered to the client via POP3, as this should correlate quite closely to the size of incoming SMTP messages and hence, has already been accounted for in the metric.