20CHAPTER 2: CONFIGURING MAIL DELIVERY
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■MX — (Optional) Select the MX check box if you need to look up the mail routes in DNS before delivery. If this is not enabled, MX records will be ignored. Generally, you do not need to select this item unless you are using multiple mail server DNS entries for load balancing/failover purposes. By checking the MX record, DNS will be able to send the request to the next mail server in the list.
■KeepOpen — (Optional) Select the KeepOpen check box to ensure that each mail message to the domain will not be removed from the active queue until delivery is attempted, even if the preceding mail failed or was deferred. This setting ensures that local mail servers receive high priority.
The KeepOpen option should only be used for domains that are usually very reliable. If the domain is unavailable, it may cause system performance problems due to excessive error conditions and deferred mail.
A list of domains can also be uploaded in one text file. The file must contain comma or tab separated entries in the form:
[domain],[route],[port],[ignore_mx],[subdomains_too],[keep_open]
For example:
example.com,10.10.1.1,25,on,off,off
The file (domains.csv) should be created in csv file format using Excel, Notepad or other Windows text editor. It is recommended that you download the domain file first by clicking Download File, editing it as required, and uploading it using the Upload File button.
