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Mail Alerting Administration

Basic Information

The OmniCenter appliance uses an onboard “send-only” email server to send its email-based alert notifications. The Mail Alerting Administration page is where you configure the settings that control the outbound email communication of this server.

To open the Mail Alerting Administration page, select ADMINISTRATION → Alerts → Mail Setup from the main menu. Each configuration section is explained below.

Mail Delivery

This section allows you to specify how email should be from OmniCenter should be handled. It allows you to choose between Direct SMTP and Relay SMTP.

OmniCenter offers two options for how outbound mail from its built-in mail server is handled.
  • Direct SMTP
    Mail is sent by looking up the DNS Mail Exchange record (MX) for the domain the alert notification is being sent to, and then trying to connect directly to that address.
  • Relay SMTP
    Forces all of OmniCenter’s outbound mail to go to the specified server first. Enter the IP address or domain name of the server in the field provided.

Netreo strongly recommends the use of Direct SMTP for the highest reliability in sending email alerts.

Click the Save Mail Setup button after making changes to this section or the changes may be lost when editing another section.

Mail Routing

Used to set up a mail routes. Only used if you have selected Direct SMTP in the Mail Delivery section. This section allows you to specify a static mail server address for a domain. Enter the domain name in the DOMAIN field, then enter the IP address that mail for that domain should be sent to in the RELAY IP field. After you have entered the domain and IP, click the blue add (+) button to save it to OmniCenter. You can add as many domains as you need.

Add static mail routes for domains whose mail server IP doesn’t match the public MX record.

Office 365 Email Authentication

If you use Microsoft Office 365 to handle your mail delivery, enter the credentials for the user account you want OmniCenter to use. OmniCenter will fail to send alert notifications if valid credentials are not provided.

If you want OmniCenter to use Office 365 for email alert notifications, you’ll need to add user account credentials here.

It’s a good idea to create a dedicated Office 365 account for OmniCenter’s use unless you have a specific reason not to.

Click the Save Office 365 Configuration button after making changes to this section or the changes may be lost when editing another section.

E-Mail Acknowledgement

This section allows you to set up OmniCenter’s email acknowledgment feature.

Enter IMAP server credentials here to be able to acknowledge email alert notifications directly through email.

Email acknowledgement allows you to directly reply to an OmniCenter-generated alert notification from your email client to acknowledge the incident the generated the alert.

Enter the details of an IMAP email account that OmniCenter can use to process acknowledgements. This will become the “from” account in all email alerts OmniCenter sends out—so it’s important that the details are correct, and that you have your organization’s SPAM filters set to permit mail from this address to pass without filtering. If you use an IP address in the IMAP MAIL SERVER field, OmniCenter’s email acknowledgement checking will not be dependent on DNS. If your IMAP server requires SSL, switch on the USE SSL option.

You can provide an alternate TCP port number to use—if one is required for your environment—in the ALTERNATE PORT NUMBER field. If this is left blank, OmniCenter will use the default IMAP ports (TCP/143 for IMAP or TCP/993 for SSL).

Ensure that OmniCenter is not prohibited from reaching this IMAP server on these ports by a firewall or access list in your environment.

Click the Save Email Acknowledgement button after making changes to this section or the changes may be lost when editing another section.

E-Mail Test

Enter any receiving email address here and click the Test Mail button to verify that OmniCenter is able to send alert notifications to that address.


When using the email test feature, the test email will always show as being from [email protected] This is merely to test the mail system and does not reflect any feature-specific “from” addresses, such as that used for email acknowledgement.

Clear Outbound Mail

If your settings are configured incorrectly, you may accumulate a number of emails in the queue that cannot be sent. Click the Clear Mail Queue button to delete these messages and clear the queue.


Mail Log

The mail log shows the most recent email activity. Click the More… link to see an expanded view of the last 50 entries added to the log.


Best Practices

Preventing Single Point of Failure Syndrome for Alert Notifications

OmniCenter includes its own send-only mail server which can be used to help prevent single point of failure syndrome when sending alert notifications.

Netreo strongly recommends the use of the Direct SMTP option when configuring the Mail Alerting Administration page for the highest reliability in sending email alerts.

If your firewall is configured to allow outbound mail traffic from OmniCenter, then action groups can be configured to send alert notifications through both an external messaging system (such as a pager or cell phone provider, or a Gmail account), as well as your internal mail system—thus avoiding a single point of failure for alert communication. These action groups can then be added as host alert contacts to your most important host devices, providing redundant alerting for host-down situations. This can be especially important for host-down alerts about your internal mail server—since, if that goes down, you won’t receive any email alert notifications from OmniCenter going through it.

When an alert notification is sent to an external email address, OmniCenter makes a direct connection to that mail provider using its built-in mail server. Provided OmniCenter’s outgoing traffic isn’t stopped by your firewall configuration, this means your alert notifications won’t be dependent on your internal mail server.

Internal Mail Server with Different IP from Public MX Record

When using Direct SMTP (the recommended option), OmniCenter sends mail by looking up the DNS Mail Exchange record (MX) for the domain the alert notification is being sent to, and then trying to connect directly to that address.

A potential problem with this is, if OmniCenter is trying to send mail to an internal email address, and your company’s internal mail server has a different address inside your firewall than the one that you get by looking up a DNS record for it. This could potentially cause an issue with mail not being sent.

If this is the case, then you have two options:

  1. The best option would be to configure your firewall to allow Direct SMTP from the OmniCenter host, then in the Mail Routing section of the Mail Alerting Administration page configure a mail route with the internal address of your mail server. Mail routing works in conjunction with the Direct SMTP setting to control where mail goes.
    • A mail route is a static address entry for a particular domain. When OmniCenter wants to send mail to “yourcompany.com” it can look in that table to get the correct internal address for the mail server, instead of using the DNS-provided address.
    • Using Direct SMTP along with Mail Routing offers the benefit of allowing you to still send alerts directly through outside providers, as well as through the internal email server—thus helping prevent single point of failure syndrome (as covered above).
  2. If your firewall blocks all outbound SMTP traffic completely unless it’s sent from your internal mail server, you can select the Relay SMTP option instead. This forces all of the mail sent from OmniCenter to go to the specified address. But, remember, this means you will be completely dependent on that system for all your outbound alerting.
Updated on February 8, 2019

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