2,311 questions
550 no mailbox by that name is currently available
![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(105.60000000000001, 17%, 20%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3ERM%3C/text%3E%3C/svg%3E)
Ronald Matias
0
Reputation points
I noticed that after setting up the hybrid exchange configuration, new mailboxes that are created on-prem are not receiving emails from external senders. All other old mailboxes on prem are getting emails just fine.
Exchange | Hybrid management
{count} votes
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Andy David - MVP 157.8K Reputation points2023-06-08T13:26:28.6233333+00:00 if you send a message to the new mailbox from an external account, what is the NDR say? Or is the message queued somewhere?
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Ronald Matias 0 Reputation points
2023-06-08T13:40:56.27+00:00 Hi Andy, here's what I get:
mx282.antispamcloud.com gave this error:
Remote server returned an error -> 550 no mailbox by that name is currently available
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Andy David - MVP 157.8K Reputation points
2023-06-08T13:48:00.5933333+00:00 Is there an anti-spam gateway in front of your Exchange server?
Where is your mx record pointing to? On-prem or 365?
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Ronald Matias 0 Reputation points
2023-06-08T13:52:16.5366667+00:00 There's no email gateway. And the MX record still points to on-prem as I haven't been able to migrate all the mailboxes to the cloud.
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Ronald Matias 0 Reputation points
2023-06-08T13:54:53.2633333+00:00 There's no email gateway. And the MX record still points to on-prem as I haven't been able to migrate all the mailboxes to the cloud.
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Ronald Matias 0 Reputation points
2023-06-08T13:57:32.58+00:00 I dont know if this will help, but only the new mailboxes created after the hybrid setup was done have this issue.
I tried migrating one of those mailboxes to exchange online, but I still get the same NDR.
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Ronald Matias 0 Reputation points
2023-06-08T13:59:12.52+00:00 Rest assured that all the basic settings were reviewed and none of them appears to cause the issue.
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Andy David - MVP 157.8K Reputation points
2023-06-08T15:05:09.2966667+00:00 what is mx282.antispamcloud.com?
Who owns that? Does this happen with messages sent from gmail and places like that?
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Ronald Matias 0 Reputation points
2023-06-11T22:35:51.67+00:00 This has now been sorted.
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![](data:image/svg+xml, %3Csvg xmlns='http://www.w3.org/2000/svg' height='64' class='font-weight-bold' style='font: 600 30.11764705882353px "SegoeUI", Arial' width='64'%3E%3Ccircle fill='hsl(41.6, 80%, 14%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EAL%3C/text%3E%3C/svg%3E)
Aholic Liang-MSFT 13,886 Reputation points Microsoft External Staff2023-06-13T06:09:12.72+00:00 Hi @ Ronald Matias，
I'm glad to hear that you've fixed this issue.
If possible, can you share your solution with us?
This will make the search for answers in the forums easier and will also benefit other community members.
Similarly, this action encourages more users to provide high-quality responses .
Thank you for your understanding and patience.
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