After migrating several users from Exchange 2010 to Exchange Online it can happen that some of the users are not able to receive e-mails from external senders.
In a normal case, you would go and check the send/receive connector settings.
You can find more info about this in the following article:
But this is not the solution in our case. The problem is, that not all of the users have this issue.
So let’s have a look on how we found out more about this issue and how to fix it:
After sending an e-mail to an user with having this problem, I received the following error Message:
If we have a closer look at this error message, we can see that there are too many hops in the request:
In our case we are running a hybrid Exchange environment. All e-mails are sent and received by a smart host.
This information tells me that something could be wrong with the routing address, so let’s have a look at it:
with this information the on premise Exchange server is able to communicate with Exchange online, again.
You can find more information about ROUTING MAIL ADDRESS here: