Configure SmarterMail as a Backup MX Server

SmarterMail is powerful enough to be used as a complete mail system that performs multiple roles from a single server, including the role of backup MX server.

In the event that the primary mail server goes down, system administrators can set up SmarterMail to function as a backup MX server to ensure users continue to receive incoming email messages. When the primary mail server cannot be contacted, email servers on the Web will attempt delivery to the backup MX server. When the primary server comes back online, the backup MX server will deliver all held email.

Applies to SmarterMail 8.x - 15.x

Before configuring SmarterMail as a backup MX server, you must ensure that the server is listening on the appropriate IP address(es):

  1. Log in to SmarterMail as the system administrator
  2. Click the Settings icon.
  3. Expand the Bindings folder in the navigation pane.
  4. Click Ports. A list of ports will load in the content pane. By default, ports 110, 143 and 25 are already set up. If necessary, add any alternative ports you may need SmarterMail to listen on.
  5. Click IP Addresses. A list of IP addresses will load in the content pane.
  6. Select each IP address you wish to listen on and click Edit. NOTE: You can only edit one IP address at a time.
  7. Select the port(s) you would like the IP address to listen on and click Save.
  8. Your server is now set up to listen on the selected ports for the IPs they have been added to.
  9. Click the Security icon.
  10. Click Antispam Administration
  11. Select the Bypass Gateway tab.
  12. Click Add
  13. Enter in the IP address of your backup MX server.
  14. Click OK to complete adding the IP.
  15. Click Save
  16. Now your primary SmarterMail server will perform IP based spam checks against the original sending server and not the backup MX

Follow these steps to configure SmarterMail as a backup MX server:

  1. Log in to SmarterMail as the system administrator.
  2. Click the Settings icon.
  3. Expand the Routing folder in the navigation pane.
  4. Click Incoming Gateways.
  5. Click New in the content pane toolbar.
  6. In the Gateway Mode field, select Backup MX from the list.
  7. Type the IP address or IP range in the appropriate field(s) for the mail server you're creating the backup MX for. (Typically, this is your primary mail server IP or IP range).
  8. Click the Spam tab and modify the spam action settings, if necessary.
  9. Click Save.
  10. Click General Settings in the navigation pane.
  11. Click the Spool tab.
  12. Change the Retry Intervals field to 10, 10, 10, 1440.
  13. Click Save.
  14. In DNS, add secondary MX records that point to the new servers IP address. Be sure to set the preference value higher than the main MX record.

All other configuration settings are optional. For more information about backup MX servers and how they work, refer to the SmarterMail Online Help. For information on using SmarterMail as a free gateway server, refer to the KB article Configure SmarterMail as a Free Gateway Server.


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Follow these steps to configure SmarterMail as a backup MX server: #8. Is the IP address or IP Range for the primary mail server or something else?
Scott Jibben (December 19, 2013 at 6:02 PM)
Scott, we edited step #8 to make it a bit clearer. Thanks!
Derek Curtis (January 8, 2014 at 4:36 PM)
If I setup Smartermail as a backup MX. How many domains could it support on this mode? Would it need any special configuration to tell the server which domains to receive email for?
Alejandro Lengua (January 21, 2014 at 1:53 PM)
If you want SmarterMail to be a back up for other server you will just repeat steps 1-10 for each domain. There is no limit or any other special configuration needed.
Brian Ward (January 22, 2014 at 10:33 AM)
Regarding Alejandro's question, if all the domains are on the same mail server and have the same IP, is there a need to repeat the steps for each domain? Seems like just repeating the steps if more than 1 IP would be more appropriate?

So, if I'm understanding correctly, let's say you had:
ServerA as Primary MX for some domains
ServerB as Primary MX for some other domains
ServerC as Backup MX for ServerA and ServerB

So you'd enter ServerA and ServerB's IP's into ServerC (ie, step #8 above).

Would that work?

Additionally, to help others and myself... when the SmarterMail gateway is selected, since the SmarterMail service can't be checked for the domains/users at the time the original (ServerA for example) is down, how often will the backup MX (ServerC) get the updated domains/users from the ServerA? And what about Forwarding addresses, does it get that too?

Help reference:
SmarterMail URL - The Webmail URL for the SmarterMail server being used an an incoming gateway. This will allow the use of Web services to verify the users and domains.

Brian Anderson (July 7, 2014 at 3:55 PM)
For adding more domains that are on the same IP you are correct you will only need to repeat the steps if the domains are on different servers.

When SmarterMail is in a gateway mode it will via web service get an update from the main server multiple times a day. If the main server is down it will go off the last updated list. As long as there are no changes between the last pull and the time the server goes down there should be no issue with receiving and holding the emails until the main server comes online.

Brian Ward (July 8, 2014 at 12:02 PM)
On my backup MX server; Routing > Incoming Gateways: I have the IP address of the primary mail server as a "Backup MX" and for the Spam tab, I have all levels set to "No Action".

However, this backup mail server will send bounce messages:
Reason: Remote host said: 554 Sending address not accepted due to spam filter

In the SMTP logs I find:
Mail rejected due to SMTP Spam Blocking: BARRACUDA, HostKarma - Blacklist, Spamhaus - XBL, UCEProtect Level 1

If spam options for this Backup MX connection is set to "No Action" why is it taking actions and rejecting these emails?

Scott Jibben (April 21, 2015 at 11:14 AM)
It sounds like you may have SMTP blocking enabled. Please check this at Security > Anti-spam > SMTP Blocking tab > Incoming Weight Threshold. When this is enabled, this will take place before any filtering action is done. Please check it out and let me know.
Andrea Rogers (April 22, 2015 at 9:07 AM)
Can i configure de BackupMX to deal as an BackupMX for other Domains which are not hosted on my primary SmarterMail-Server? i.e. Customer has an own Postfix-server at provider A and ask me to play the BackupMX in our datacenter (not provider A)?
WebControl GmbH (May 15, 2015 at 8:51 AM)
Can the free edition of SmarterMail be used as a backup MX server for a primary mail server running a paid version of SmarterMail? Or is a license required to allow for the backup server to store multiple domains' messages in its spool?
Eric Van Pyrz (February 25, 2016 at 3:29 PM)
Hi Eric! Yes, you can use the free edition of SmarterMail as a backup MX server for a paid version.
Andrea Rogers (February 26, 2016 at 8:53 AM)
I am not sure if my backup MX server is working. Is there a way to verify it is working, checking logs or reports? I do have the Enterprise edition of SM. I have Enable Smartermail Gateway checked, on the Gateway tab I have my URL, admin username and password. If I disable Smartermail on my primary sever I am not sure how long I need to disable it to test it. I do have several IPs on my primary server and I have included them as incoming gateways, Backup MX. I also added the secondary MX records to my domains.
Patrick Mattson (August 7, 2016 at 7:51 PM)
Hey Patrick! You can perform a test to ensure your backup MX server is working by telnetting to your backup MX server and typing up a quick email for a recipient on the primary server. The backup MX server should accept the message, and deliver it to the primary at that point. This allows testing without downing any service. More information can be found here:
Andrea Rogers (August 9, 2016 at 9:53 AM)

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