D-Link NetDefendOS User Manual page 94

Consecutive sent emails cannot have less than this amount of elapsed time between them.
The value of this property can prevent emails being sent too often.
If an email is ready to send but cannot because it is within this period of time, any new events
will be added to the email until this period has expired.
Advanced Options
• Identity
This string parameter identifies the SMTP client in the HELO or EHLO command sent to the
SMTP server by NetDefendOS. If this property is not set, NetDefendOS will set this
automatically to the IPv4 address of the NetDefendOS interface that sends to the SMTP
server.
• X-Mailer
This is the name of the software that is communicating with the SMTP server. This is optional
and is left blank by default.
Mail Alerting Processing Flow
To better explain the settings for the event trigger properties, consider the following example: a
Mail Alerting object has been configured in NetDefendOS and the Multiple events trigger option
has been selected with a Event count period value of 2 minutes and an Event count threshold value
of 3 events (in other words 3 events must occur in a 2 minute window for an email to be sent).
Assume that since sending its last email, 6 log events occur that are eligible for mailing and these
occur over a 6 minute period of time. The diagram below divides the 6 minutes into 2 minute
sections for clarity and shows when the events occur.
The processing flow is as follows:
1. NetDefendOS starts counting the events from zero before the 1st event.
2. The 3rd event occurs, reaching the threshold. However, the 1st event is outside the 2 minute
time window and only the 2nd and 3rd events are inside the time period so an email is not
sent.
3. This is also the case for the 4th and 5th events. There are not enough other events in the
previous 2 minutes for either to reach the threshold of 3.
4. Only when the 6th event occurs is the threshold of 3 events reached within the previous 2
minutes and an email is sent (after waiting the Keep collecting before sending number of
minutes during which time any new log events will be added to the email).
5. NetDefendOS drops the 1st, 2nd and 3rd events so these are not included in the email.
Chapter 2: Management and Maintenance
94