Forum Discussion

Brass Contributor

Jan 08, 2020

Migrated Mailbox Able to Send but not Receive

Hello, We have recently setup a full hybrid exchange environment using Microsoft's Hybrid Exchange tool. I've created a test mailbox, setup some calendar items, sent and received some email b...

Brass Contributor

Jan 08, 2020

CloudHalyou are indeed correct that the Hybrid Configuration Wizard has created the send and receive connectors in both Office 365 and EOP.

I am not too sure how they should be setup. Initially I chose the "Configure my Client Access and Mailbox servers for secure mail transport (typical)" option, however there is another option for "Configure my Edge Transport servers for secure mail transport"

Should I be using the second option to have mail flow through EOP?

On the second page it has me choose EOP to host receive connectors for secure mail transport, and I picked the only option available:

Everything else goes through fine and it doesn't show any sign of error, however the mailbox is still unable to receive.

Looping back to my original point, might it have anything to do with the send connector in EOP (Outbound to Office 365 rule)?

The MX record is set to Mimecast, which then directs to EOP, however if it's trying to use the send connector, won't it just create an infinite loop of sending to itself?

Would I need to set a smart hosts to Office 365 instead?

Thanks again!

CloudHal

Iron Contributor

Jan 09, 2020

Hi there, you need an understanding of how mail routing between on-prem users, and migrated online users works. It doesn't create a mail loop because it uses an internal routing domain which is @yourtenant.mail.onmicrosoft.com. This is explained here https://docs.microsoft.com/en-us/exchange/transport-routing in the section called Route incoming Internet messages through your on-premises organization.

So the outbound connector to O365 is limited to this domain, and your migrated user should have a TargetAddress @yourtenant.mail.onmicrosoft.com. So if you send an email to this user, Exchange knows the user has been migrated due to the target address, and sends the email through the O365 send connector. I would look at your migrated user to see if they have been migrated correctly, if so the targetaddress attribute will be set. You should also see them in the ECP on-prem showing as Office 365 mailbox.

Unit2777
Brass Contributor
Jan 10, 2020
CloudHalthanks for taking the time to respond.

I forgot I had this thread open, but I have managed to resolve the issue.

I was getting a connection refused error when trying to validate the connectors even when I had whitelisted all of the IPs from https://docs.microsoft.com/en-us/office365/enterprise/urls-and-ip-address-ranges#exchange-online
(Note: I was unable to add the hostnames to our firewall as I was told it doesn't support it and/or wildcards.)

In the end, we opened up ports 25 and 443 to all IP ranges, and it worked.
Not ideal but at least it is working for the time being, so I guess I just have to get this migration done quickly!

Thanks again.