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Backup mailserver emails are dropped
Question asked by Gijs van der Velden - May 31, 2015 at 3:25 PM
Unanswered
I've recently noticed that some of the incoming mail is being dropped, from certain domains.
 
I had two mx records,
1. my smartermail server with greylisting
2. a backup mx server provided by my domain registrar.
 
What happened is that because of the greylisting some of the mail would go to the 2nd mail server.
This mail would then be send to my smartermail server from the 2nd mail server.
This mail appears to be dropped because it came from my 2nd mail server and not from the original mail server.
I assume this happened because of dmarc and or spf rules.
 
I've currently disabled greylisting, but if my mail server go's down those mails would still be dropped.
How can I configure a server as a trusted backup mail server in smartermail? (so that dmarc and spf rules are ignored when mail comes from that server)

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Bruce Barnes Replied
May 31, 2015 at 9:33 PM
The backup MX server is not properly configured.
 
Greylisting should never send anything to a backup MX server.
Bruce Barnes
ChicagoNetTech Inc

Phone: (224) 444-0169

E-Mail and DNS Security Specialist
Network Security Specialist

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Web and E-Mail Hosting, E-Mail Security and Consulting
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CCWH Replied
May 31, 2015 at 10:33 PM
I'd say the sending mailserver MX isn't correctly configured in some way, however I have seen incoming mail be asked to retry in x seconds and it then jump straight to the backup MX and retry there instead. I only saw this on Friday with an incoming domain migration. Where we had our main MX (0), backup MX (10) but incorrectly left the old MX (20) within the records. We saw a test mail from Outlook.com try MX 0, then MX 10, both being asked to retry in 60s due to greylisting.... The mail then ended up being delivered to the old mail server (MX 20). To the OP, I would suggest adding your providers backup MX to your smartermail backup MX configuration: https://portal.smartertools.com/kb/a2668/configure-smartermail-as-a-backup-mx-server.aspx

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