Internal E-Mails landing in Exchange 365 mailbox instead of external mailbox

Question

Internal E-Mails landing in Exchange 365 mailbox instead of external mailbox

Timm Beckmann 21

Hi,

we have the following problem.

We have installed a domain example.com with the InternalRelay setting, because we want to use an external hosters mailboxes. Strato.de

For a certain user, when an internal user sends a mail from usera@ssss .com to the user userb@ssss .com, the mails are landing in the exchange 365 mailbox instead of the Strato mailbox.
External emails are correctly landing in the Strato mailbox.

For Strato we have set the Mailsettings to:
No SPF rules
"v=spf1 include:spf.protection.outlook.com redirect=_spf.strato.com"

EDIT:
The MX Record on Strato is set to the Strato Mailserver.
smtpin.rzone.de 81.1xx.1xx.9x
smtpin.rzone.de 2axx:2x:x2xx:2xx:5xx0::1097

I added the domain in the 365 admin center, set most DNS settings as advised and got it in.
There are no other configurations that I know of or can see, aside from the "Internal Relay" setting that I used in the Exchange Admin panel.
Two DNS settings are different, than what microsoft wants me to have:
TXT expected
v=spf1 include:spf.protection.outlook.com -all
vs what I have
v=spf1 include:spf.protection.outlook.com redirect=_spf.strato.com

MS expected
example-com0e.mail.protection.outlook.com
vs what I have
smtpin.rzone.de

We have no connectors of any kind defined right now.

EDIT2:
For now, we have made a forward from Strato to the exchange mailbox via the onmicrosoft alias and the users now uses the exchange mailbox instead.
However that's only a current fix, until we know how to get it to work via the Strato mailbox.

Which additional information do you need?
Which settings could we search for, that could explain this behaviour?

Greetings
Timm

Andy David - MVP 157.8K Reputation points MVP Volunteer Moderator

2022-10-09T15:12:37.687+00:00

How are messages being routed? Is there a contact that forwards or a send connector or a send connector routing to the strator namespace?
Timm Beckmann 21 Reputation points

2022-10-09T17:21:33.09+00:00

Well we have not defined any connectors or anything. Also there is no special forwarding set somewhere, that I know of.

While looking up something, thanks to your comment I have found a certain systematic, that could explain the weird behaviour.

Some users have used the Exchange Login in Outlook to receive and send mails: userx@ssss .com
The login for the Strato mail server is also userx@ssss .com. However there you have to use IMAP settings of strato.

The person using the Exchange Login, gets and receives all mails in the Exchange Mail account. Interestingly also external e-mails.

However, the person, using the Strato IMAP settings, only receives the external e-mails, while all internal e-mails are sent to their Exchange mailbox.

So now, we have to figure out how to send internal mails for users using the Exchange Login to the Strato mailbox for the person using the Strato IMAP settings.
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff

2022-10-20T08:10:18.037+00:00

Hi @Timm Beckmann ,
It has been a few days and I am checking in to see how things are going on with this issue.
Does this issue have any updates? If it has been resolved, please click "Accept as answer" to mark useful post or share your solution, your action would benefit others who have similar issues. If you have any questions or need further assistance, please feel free to post back. Thanks!

Accepted answer

1 additional answer

Your answer

Andy David - MVP 157.8K Reputation points MVP Volunteer Moderator

2022-10-09T15:12:37.687+00:00

How are messages being routed? Is there a contact that forwards or a send connector or a send connector routing to the strator namespace?
Timm Beckmann 21 Reputation points

2022-10-09T17:21:33.09+00:00

Well we have not defined any connectors or anything. Also there is no special forwarding set somewhere, that I know of.

While looking up something, thanks to your comment I have found a certain systematic, that could explain the weird behaviour.

Some users have used the Exchange Login in Outlook to receive and send mails: userx@ssss .com
The login for the Strato mail server is also userx@ssss .com. However there you have to use IMAP settings of strato.

The person using the Exchange Login, gets and receives all mails in the Exchange Mail account. Interestingly also external e-mails.

However, the person, using the Strato IMAP settings, only receives the external e-mails, while all internal e-mails are sent to their Exchange mailbox.

So now, we have to figure out how to send internal mails for users using the Exchange Login to the Strato mailbox for the person using the Strato IMAP settings.
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff

2022-10-20T08:10:18.037+00:00

Hi @Timm Beckmann ,
It has been a few days and I am checking in to see how things are going on with this issue.
Does this issue have any updates? If it has been resolved, please click "Accept as answer" to mark useful post or share your solution, your action would benefit others who have similar issues. If you have any questions or need further assistance, please feel free to post back. Thanks!

Answer 1

Hi @Timm Beckmann ,
Sorry for the late reply. I have revisited the information you provided and rearranged my thoughts.

Currently, all users have mailboxes in the Exchange online environment and Strato mail server, using the same domain name and the same email address.
However, some users need to use a mailbox on the Strato to receive mails from Exchange online.
The problem now is that mailboxes on Exchange can't send messages to mailboxes that have the same name on external server.
According to the description of the internal relay type of the accepted domain in the exchange.

Email is delivered to known recipients in Office 365 or is relayed to your own email server if the recipients aren't known to Microsoft 365 or Office 365.

Please try to create a mailbox without duplicate names on an external Mailbox server and send test mail from Exchange to this mailbox to see if it works.
If it can be successfully sent to the external mailbox, I would suggest that you could change the email address that need to use to the external server to a different address than exchange internal. Then, create automatic forwarding to the mailbox on the external server.

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
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Timm Beckmann 21 Reputation points

2022-10-25T18:19:20.493+00:00

Thank you.
Thanks to your suggestion, I just made a forward in exchange to an alias set on Strato, that's different than the Exchange mailbox mail.
It works.

Answer 2

Aholic Liang-MSFT 13,886 Microsoft External Staff

Hi @Timm Beckmann ,
Can you tell us how did you configure Mx record and your accept domain?
Did you create a connector to relay emails to your own Strato server?

Please refer to the following links to configurate your accept domain and connector to see if it works：
Manage accepted domains in Exchange Online | Microsoft Learn
Set up connectors to route mail between Microsoft 365 or Office 365 and your own email servers | Microsoft Learn

If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

Timm Beckmann 21 Reputation points

2022-10-13T18:26:55.207+00:00

Hi @Aholic Liang-MSFT ,

The MX Record on Strato is set to the Strato Mailserver.
smtpin.rzone.de 81.1xx.1xx.9x
smtpin.rzone.de 2xxx:2xx:2x:2x02:5xx0::1097

I added the domain in the 365 admin center, set most DNS settings as advised and got it in.
There are no other configurations that I know of or can see, aside from the "Internal Relay" setting that I used in the Exchange Admin panel.
Two DNS settings are different, than what microsoft wants me to have:
TXT expected
v=spf1 include:spf.protection.outlook.com -all
vs what I have
v=spf1 include:spf.protection.outlook.com redirect=_spf.strato.com

MS expected
example-com0e.mail.protection.outlook.com
vs what I have
smtpin.rzone.de

We have no connectors of any kind defined right now.
I tried to define a new connector in the admin exchange panel from 365 to the mail server Strato.
I can only assume some settings, so I chose to apply it for all accepted domains and tried
strato.de
as Smarthost and alternatively the ip above.
Unfortunately the testmail still landed in the 365 exchange mailbox instead of the Strato one. So this didn't seem to work at all.

Writing you all this, maybe I just have to change the spf TXT around?
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff

2022-10-14T09:39:32.24+00:00

Hi,
I want to confirm whether user c is the same as user b, it has a mailbox in your Exchange 365 environment?
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff

2022-10-14T09:39:56.613+00:00

Hi,
I want to confirm whether user c is the same as user b, it has a mailbox in your Exchange 365 environment?
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff

2022-10-14T09:41:13.03+00:00

Hi,
I want to confirm whether user c is the same as user b, it has a mailbox in your Exchange 365 environment?
Timm Beckmann 21 Reputation points

2022-10-14T18:16:59.497+00:00

Hi,

Yes all users, a, b and c have mailboxes in Exchange 365 after we gave them a Microsoft 365 Business Standard License.
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff

2022-10-17T09:45:31.123+00:00

Hi，

The MX Record on Strato is set to the Strato Mailserver.

This seems to be the issue. Because the Mx record point to the Strato Mail server, creating the relay connector on Exchange is not valid.
Please setting the internal relay on Strato Mail server to see if it works.
Or, set the MX record to point to the Exchange online, and then create the relay connector on Exchange online again.
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff

2022-10-17T09:45:47.83+00:00

Hi，

The MX Record on Strato is set to the Strato Mailserver.

This seems to be the issue. Because the Mx record point to the Strato Mail server, creating the relay connector on Exchange is not valid.
Please setting the internal relay on Strato Mail server to see if it works.
Or, set the MX record to point to the Exchange online, and then create the relay connector on Exchange online again.
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff

2022-10-20T05:52:49.473+00:00

Hi,
It has been a few days and I am checking in to see how things are going on with this issue.
Does this issue have any updates?
If you have any questions or need further assistance, please feel free to post back. Thanks!
Timm Beckmann 21 Reputation points

2022-10-20T18:32:08.087+00:00

Currently the mails are functioning for all external mails going to Strato and Strato forwarding those on the onmicrosoft alias to the 365 exchange mailboxes.
Internal 365 mails are directly sent to the exchange mailboxes.

If we set the MX mail server to a different one e.g. exchange, then the mails are not going to Strato anymore but to exchange server.
Then the Strato mailboxes wouldn't work anymore.

The problem is, that when setting a connector in exchange, the mails from 365 are still landing in exchange mailboxes, but not in Strato.
So "Because the Mx record point to the Strato Mail server, creating the relay connector on Exchange is not valid"
I don't understand that. Regardless of what mail server is set, the connector should send the mails to where the connector says to send them to, no?
So when setting the exchange as mail server, the problem would get worse, as now all e-mails are going to exchange?

So the problem is the other way round. Even though the Strato mailserver is set, the internal mails are not going where they should.

"Please setting the internal relay on Strato Mail server to see if it works."
I don't understand that. Where do I set any relay to the Strato Mail server?

Also just checked. The spf1 settings are only for spoof protection, so they shouldn't to anything in this regard.

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Internal E-Mails landing in Exchange 365 mailbox instead of external mailbox

1 additional answer

Your answer