Azure Email Communication Services delivery suppressed MailboxUnavailable while mailbox is reachable (SmtpStatusCode 550)

wstaelens 41

Some of the emails sent via Azure Email Communication Services were never delivered.

The log file below (i changed to emails to foo@bar.be and foo2@bar2.be and domain to something.net)

{"OperationType":"DeliveryStatusUpdate","OperationCategory":"EmailStatusUpdateOperational","RecipientId":foo@bar.be,"DeliveryStatus":"Suppressed","FailureReason":"MailboxUnavailable","FailureMessage":"Email sent to foo@bar.be was suppressed due to a known delivery failure: 550 .","SmtpStatusCode":"550","SenderDomain":"something.net","SenderUsername":"donotreply","IsHardBounce":true}

{"OperationType":"DeliveryStatusUpdate","OperationCategory":"EmailStatusUpdateOperational","RecipientId":foo2@bar2.be,"DeliveryStatus":"Suppressed","FailureReason":"MailboxUnavailable","FailureMessage":"Email sent to foo2@bar2.be was suppressed due to a known delivery failure: 550 .","SmtpStatusCode":"550","SenderDomain":"something.net","SenderUsername":"donotreply","IsHardBounce":true}

The mailboxes, let's call them foo@bar.be and foo2@bar2.be which never received the emails work normally. When I send emails to them they arrive correctly.

Only when emails are being sent from Azure Email Cummunicaiton Services they are never delivered to foo@bar.be and foo2@bar2.be . (Other emails sent from Azure Email Communcation Services are delivered correctly at other domains).

What could be the reason these two specific email accounts never receive emails sent via Azure Email Communication Services?

In the Azure logs I see "MailboxUnavailable" but when I send a test email from my Hotmail or another account they are successfully delivered at foo@bar.be and foo2@bar2.be. So it is strange that it reported as "MailboxUnavailable"...

Note: The foo@bar.be and foo2@bar2.be email accounts are actually configured as forwarders in DirectAdmin (they are not real mailboxes) But this has never been a problem before and email always arrived correctly.

any suggestions?

VenkateshDodda-MSFT 20,536 Reputation points Microsoft Employee

2024-03-18T09:05:59.7933333+00:00

@wstaelens Thanks for reaching out to Microsoft Q&A, apologize for any inconvenience caused on this.

Thanks for your response, the right help to get the issue investigate is support I would suggest you file a support case from the subscription where the issue and resource is present.

In case if you are facing any issues, I have reached out to you over private message could you please check and help us with requested details to check further.
Natalie van Gogh 0 Reputation points

2024-04-26T07:49:59.4866667+00:00

Did you ever find out what the issue was. I am facing the same issue
Rodrigues,Diego 5 Reputation points

2024-06-27T19:20:26.3+00:00

Facing the same issue with few users.
wstaelens 41 Reputation points

2024-07-02T07:22:51.1333333+00:00

@Rodrigues,Diego @Natalie van Gogh we found out it is related to where the receiver has hosted their mailbox. Some of my receivers had email forwarders configured at a local hosting firm. They were using DirectAdmin for the email forwarders. And that mailserver of the hosting firm blocks/drops these emails with smtpstatuscode 550. Nothing you can do about.... You can only ask them to complain to their hosting or switch to e.g. office 365 for mail.

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Azure Email Communication Services delivery suppressed MailboxUnavailable while mailbox is reachable (SmtpStatusCode 550)

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