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use of smart hosts to forward secondary domains

smart hosts

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#1 Matt King

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Posted 24 October 2018 - 11:31 AM

We are currently in a hybrid deployment of O365 with on-prem exchange 2010.  We are having an issue getting an internal secondary domain through the barracuda spam filter.  The email gets accepted but then rejected because we don't allow smtp relaying.  


We are considering creating a smart host entry on the barracuda to accomplish our request.  Would this be the best way to accomplish this without enabling smtp relaying?



local domain:  domain.com

secondary domain:  a domain.com

emails are coming in from MS O365 to the barracuda through a internal-relay domain


current internal exchange 2010 server uses a smart host relay to forward internal messages to the secondary domain.

#2 Scott Kuntz

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Posted 24 October 2018 - 11:37 AM

Hi Matt,


It would be best to phone in and open a case with us so we can look at the setup further and assist you with getting this working.


Scott Kuntz

Barracuda T2 Support Engineer

#3 Matt King

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Posted 25 October 2018 - 10:41 AM

HI Scott,


So I initially opened a ticket/case with Barracuda case #03054800.  I spoke to someone and we went through using a relay through trusted IP address, adding a new domain, and enabling SMTP relay, which all are not what I was looking for.  The technician then said that using a smart host would theoretically work, but I just wanted to confirm with someone who may have done that before.  Only internal users would be sending emails to this domain (internal exchange and O365).  



#4 Dana Morris

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Posted 08 February 2019 - 09:31 AM

HI Matt, 


I am curious if you ever determined a resolution.  We recently migrated from on-premise Exchange/on-premise Email Security 310 to O365 and Email Security Cloud.  We are attempting to set up a relay from Barracuda to our email encryption provider, Zix.  We have received conflicting reports from Barracuda support on whether or not this can be done (2 techs no, 1 tech yes).  


I can see where this would have been setup in the on-premise appliance, but 2 support tickets later am unable to determine where/if this can be done in Email Security Cloud.  


Any insight is appreciated! 

#5 Matt King

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Posted 08 February 2019 - 09:44 AM

Hi Dana,


We ended up creating a smart host rather than using SMTP relay and our device is a on-premise appliance.