Exchange Hybrid - On-Prem mailboxes can't send to Online mailboxes

Copper Contributor

We're now running Exchange Hybrid

OnPrem: Exchange 2019 latest patch.

 

On-Prem mailboxes are not able to communicate with mailboxes in Exchange Online in any way. The other way around is working fie though.

 

Mailboxes on-prem:

The communication to Exchange Online mailboxes isn't working >

Can't send emails to Exchange Online mailboxes, or see free busy of Exchange online mailboxes and can't send calendar invites.

 

Mailboxes in Exchange Online:

  • Receive emails from external sent to: email address removed for privacy reasons - working.
  • Receive emails from external sent to: email address removed for privacy reasons - working.
  • Receive emails form external setn to: email address removed for privacy reasons - NOT working.
  • Receive emails from internal on-prem mailbox - NOT working. No matter to which domain it is sent.
  • Calendars: Users can fully see on-prem calendars and can also send invites.
  • Send emails to external and internal - working.

 

The Exchange on-prem queue shows:

DeliveryType: DnsConnectorDeliver

Status: Retry

NextHopDomain: cadomain.mail.onmicrosoft.com

 

The bounce back emails the on-prem mailbox receives when trying to send to a mailbx that is online:

 

Server at cadomain.mail.onmicrosoft.com (104.47.75.164) returned '400 4.4.7 Message delayed'
3/24/2023 3:38:01 AM - Server at cadomain.mail.onmicrosoft.com (104.47.75.164) returned '450 4.4.316 Connection refused [Message=Socket error code 10061] [LastAttemptedServerName=cadomain.mail.onmicrosoft.com] [LastAttemptedIP=104.47.75.164:25](Socket error code 10061)'

 

 

This is the on-prem Exchange delivery report:

Delivery Report for usernametest2 ‎(usernametest2(at)domain.ca)‎


Submitted3/24/2023 9:25 AM EXCHANGE2019
The message was submitted to on-premExchange.domain.local.


Pending
3/24/2023 9:25 AM on-premExchange.domain.local
Message was received by on-premExchange.domain.local from on-premExchange.domain.local.

 

3/24/2023 9:25 AM on-premExchange.domain.local
The e-mail address for recipient "usernametest2(at)domain.ca" was updated to the e-mail address "usernametest2(at)cadomain.mail.onmicrosoft.com". The message is in the process of being delivered.


Submitted
3/24/2023 9:27 AM on-premExchange.domain.local
The message was submitted to on-premExchange.domain.local.


Pending
3/24/2023 9:28 AM on-premExchange.domain.local
The e-mail address for recipient "usernametest2(at)cadomain.mail.onmicrosoft.com" was updated to the e-mail address "usernametest2(at)domain.ca". The message is in the process of being delivered.

 

3/24/2023 10:40 AM on-premExchange.domain.local
Message delivery is taking longer than expected. There may be system delays. For more information, contact your email admin.

6 Replies

@Lussy150 

 

Sorry for the inconveniences or delays this issues may have caused you. To start troubleshooting, can we get more information about the issue? 

 

1. When it started? 

2. Did you just start sending to Exchange Online from this IP?

 

Exchange Online will grey list and back off connections it hasn't seen before in some cases. Especially if they are "spammy" in nature. Usually, after that initial back off period or when a contact is placed to Microsoft, EOP will allow these and they will go through. 

 

If this is something that just started occurring, then you can removing and re-adding the send/receive connector. 

 

Thank you!

 

If I have answered your question, please mark your post as Solved

If you like my response, please give it a Like :smile:

Appreciate your Kudos! Proud to contribute! :)

 

We only just ran the HCW a day ago, to move to Hyrbrid. So in that sense, yes it just started and we just started sending data to Exchange Online.

 

You suggest manually removing the send connector in Exchange on-prem and the receive connector on Exchange Online and then re-add them?

 

Would just disabling/enabling do the trick as well?

 

Oh and mailboxes can successfully be migrated from on-prem to Exchange Online. So that works too right now as well.

@Lussy150 

 

Thank you for your prompt response. I am glad I was able to provide a fix to the issue you are having. You can reach out to me if you need further clarification or assistance.

 

Kindly mark your post as solved and please give it a like too. 

If I have answered your question, please mark your post as Solved

If you like my response, please give it a Like :smile:

Appreciate your Kudos! Proud to contribute! :)

 

Hi RecepGencaslen,

the issua is not resolved. Not sure where in my previous post I implied that it was resolved. The fact that the mailboxes can be migrated, was provided as additional information that may be valuable to find a resolution.

@Lussy150It sounds like an issue with either the send connector to Office 365 in your on-prem Exchange organisation or the "your org to Office 365" connector in EXO. Confirm that your Exchange server can make an SMTP connection to Exchange online. I'd guess the connection is being blocked...either by your network or because the certificate is incorrect and EXO is rejecting the connection (you can use certificates or IP addresses to identify the on-premises Exchange server making the connection)

Hello,
It seems that your public IP address has been greylisted by Exchange Online environment. You can try to change your outgoing mails public IP address to confirm. However this change also requite to review the connectors and SPF as well.

You can also add your Public IP addresses to the Exchange Online Protection whitelist.

Thanks
Srikant