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550 5.1.10 RESOLVER.ADR.RecipientNotFound

After adding a domain to O365 tenant, getting a bounce back when emailing from domain already in O365. So @domaina.com is already in O365 and we are planning to setup a Hybrid Exchange 2010 with domainb, so when domainb is added to O365 and a user@domaina.com emails him he gets a bounce back. We have not setup the Hybrid yet as the server still needs to be patched to SP3. I tried setting domainb to Internal Relay in O365 so it would look for the MX records but still get the same error. Do I need to setup a connector with the Exchange server?

Original Message Details
Created Date:      3/6/2018 7:32:24 PM
Sender Address:      user@domaina.com

Recipient Address:      user@domainb.com

Subject:      Test

Error Details
Reported error:      550 5.1.10 RESOLVER.ADR.RecipientNotFound; Recipient user@domainb.com not found by SMTP address lookup
DSN generated by:      DM5PR19MB0954.namprd19.prod.outlook.com

Thanks

timgreen7077

I'm not clear. Are both domains already in O365 or just domaina.com?

abhijitm00

ASKER

Domaina is already in O365 with MX record pointing to O365. Domainb was added in preparation for Azure AD Connect and Hybrid setup. Domainb has MX record pointing to Barracuda appliance

SOLUTION

timgreen7077

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timgreen7077

just for clarification on the send connector, when you create it instead of using * you will use doaminb.com

abhijitm00

ASKER

Got it I will try that

timgreen7077

good luck.

abhijitm00

ASKER

Hi Tim, I am getting the following error when trying to setup a connector to on-prem Exchange server:

Reason: [{LED=450 4.4.316 Connection refused [Message=Socket error code 10061] [LastAttemptedServerName=1.1.1.1] [LastAttemptedIP=1.1.1.1] [CY1NAM02FT007.eop-nam02.prod.protection.outlook.com]};{MSG=Socket error code 10061};{FQDN=1.1.1.1};{IP=1.1.1.1};{LRT=3/6/2018 9:38:38 PM}]. OutboundProxyTargetIP: 1.1.1.1.

Would this have something to do with firewall? We have not restricted smtp to any particular IP range and it is set to any as of now

Thanks

timgreen7077

did you use a smart host or anything when you setup the new connector. If so don't use a smart host in o365. can you send me the settings you set on the new connector?

abhijitm00

ASKER

Yes I specified the IP address of the on premise Exchange server

timgreen7077

Ok, disable the connector you created. When you are in o365 looking at the connectors, do you see any connectors that are enabled or are there no connectors.

abhijitm00

ASKER

There are no connectors and I could not create a connector without specifying a smart host or an IP

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timgreen7077

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abhijitm00

ASKER

Barracuda and that send the email to Exchange server

timgreen7077

Ok, point the connector to the barracuda public IP address not the Exchange server.

timgreen7077

It should allow you to validate also the make sure it connects.

abhijitm00

ASKER

Thanks I will try that

abhijitm00

ASKER

Hi Tim, I was able to setup a connector to on-prem Exchange server and the email flow started working. I was trying to add an incorrect IP address. Thanks for your assistance

timgreen7077

Excellent. Take care and good luck on your O365 setup.