MXBackup server stopped queueing mail
Question asked by Ray Cook - 1/27/2016 at 12:47 PM
We have SM 14running as MX Backup server. All was well in that there were usually a few messages in there and some passed through to the  main server which then handled the spam checking etc. All domains have a secondary MX set up pointing to the mxbackup server
I know not everyone agrees the need for a backup server but we have found that if the mail server is down it's the a good way to queue email and then send them thru when the server is back online.
recently we placed both servers behind a dedicated firewall and we changed the IP of the main mail server. Whilst we were moving the mail server to its new location, we expected the backup server to start queuing mail. But nothing ever came thru. And it must have been like that since we moved it behind the firewall but never noticed.
In fact, we needed to change the bindings to the new internal IP for all the ports. When I did that the logs started reporting incoming connections. They were all rejected even when the email address was a valid email address on the main server.
I am sure that at one time emails sent to valid users would be sent thru by the mxbackup. It's a spam trap but not a lot gets through.
So I decided to add the smart gateway option and webservices to the incoming gateway record using the main server admin and email and its web address - but that doesn't seem to work either. The logs show 'user does not exist' for valid emails on the main server. This means that if the main server goes down, all mail we be rejected by the back up server? Or does it somehow know it has to queue them?
Any ideas anyone?

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Bruce Barnes Replied
When you moved your servers to behind the firewall, did your PUBLIC IP addresses change?  If so, were those changes made in your SmarterMail configuration, to point the PORT MAPPINGS to the new PRIVATE IP ADDRESS, assigned by the firewall or router, and making certain you have a proper HOST to PUBLIC IP ADDRESS mapping in SmarterMail?
If your public IP addresses changed, did you update the A records in your DNS? 
If your public IP addresses changed, did you update your rDNS?
If your public IP addresses changed, did you update the changes in the BACKUP MX server configuration in SmarterMail?
Bruce Barnes
ChicagoNetTech Inc

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Ray Cook Replied
Hi Bruce, thanks for the reply. My question was a bit garbled.

Two servers.

1. Main mail server had an IP change as it was physically moved behind dedicated firewall
2. MX backup put behind that firewall prior to the main server move, but no IP change required.

So the MX Back up did not require external IP changes to DNS but DID require internal mapping in SM config to the new internal IP - this is the step I forgot several days ago and would have rendered the backup server useless - but I didn't notice

Main server moved on 26th Jan without a hitch, all working fine, all DNS external and internal mappings ok.

During the move I expected email to queue to the backup - but it didn't because I had not done the mappings as outlined above.

After the main server move, I discovered this after some head scratching and made the changes, then I expected the usual spam to appear in the queue and the odd email to be forwarded to the main server (I did remember to add a new incoming server gateway!) Nothing.

I had never used the Smart gateway before. It just all worked (having said that, the mail server has been up continually for months, so problems may have been lurking unnoticed).

So, now I had corrected my omission I noticed at least the logs were being created, but all mail, even that for addresses on the main server that were valid, were being rejected. So a little more head scratching and an attempt to look at historic logs to see if this was always the case, but, unfortunately, we only keep logs on the backup server for 3 days.

So, I thought, maybe I should try Smart Gateway, I set it up, but no change, No emails getting to Spool.

Now I'm thinking, well, maybe that's right and only when the main server is down will valid emails be queued. I just cannot find enough info. and guidance on this from SM - there seems to be a dearth of detail.

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