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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(262.40000000000003, 19%, 35%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EA%3C/text%3E%3C/svg%3E)
Our SMTP receive log shows an error every thirty seconds. SMTP traffic appears to be flowing fine from on-premise to O365/Exchange Online, but some users periodically report the following error:
the server response was: 4.7.0 Temporary server error. Please try again later. PRX5.
SMTP Receive Error Log:
2024-08-08T12:54:03.845Z,,08DCA9486495F762,0,127.0.0.1:25,127.0.0.1:43100,+,,
2024-08-08T12:54:03.845Z,,08DCA9486495F762,1,127.0.0.1:25,127.0.0.1:43100,>,421 4.3.2 Service not available,
2024-08-08T12:54:03.845Z,,08DCA9486495F762,2,127.0.0.1:25,127.0.0.1:43100,-,,Local
I have searched the web and found that this type of error could be caused by a misconfiguration where SMTP emails are not received or sent at all. However, SMTP traffic is flowing as expected. Could there be a secondary listener that needs configuring? Any suggestions for resolving this issue would be appreciated.
![](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(44.800000000000004, 43%, 14%)' cx='32' cy='32' r='32' /%3E%3Ctext x='50%25' y='55%25' dominant-baseline='middle' text-anchor='middle' fill='%23FFF' %3EBJ%3C/text%3E%3C/svg%3E)
Hello, @Anon4343
It's been a long time since I've heard from you, have you solved your problem yet? Did my previous reply help you？ If it was useful, you can mark it as an answer. Thank you for your understanding and support.
Sorry for the late response. My account was incorrectly flagged and suspended.
Hi，@Anon4343
M365 backend team can assist with an on-prem hybrid Exchange Server.
Here's how to contact the M365 team:
Hi，@Anon4343
Thanks for posting your question in the Microsoft Q&A forum.
To fix this issue, you can be done in 2 steps.
Step 1: Add a custom receive connector to Office 365 IP for Port 25.
Step 2: Bind the SSL Certificate to three receive connectors: default, default frontend, above-mentioned custom receive connector.
Thanks Bruce. Sorry for the delay.
The certificate is already assigned to each of the protocols.
Thanks Bruce.
Hi, @Anon4343
I'm glad to hear back from you.
What do you mean by “My account was incorrectly flagged and suspended.”? Is it your account that is unable to log into the forums? If not, can you provide a specific screenshot?
Did the problem persist after you set it up?
Can you provide error reporting information if the problem still exists?
Another associate was able to help me restore access to my account. Something in the error log was being flagged.
I have not made any changes to the Exchange environment. All suggestions were already configured.
Hi, @Anon4343
Perhaps my expression gave you a misunderstanding. Did the problem still occur after you set it up as I suggested?
If the problem still occurs , can you provide specific information or screenshots?
What you had suggested was already configured.
Hi，@Anon4343
I've learned about your setup and I have a few questions I need to confirm.
1.Does the problem persist? If the problem still occurs , can you provide specific information or screenshots?
2.Does this error affect your use?
Hi，@Anon4343
It is recommended to open a service request to M365 backend team to resolve this issue. Thanks for your understanding。
Would the M365 backend team assist with an on-prem hybrid Exchange Server?
Very good. I'll contact them. Thanks.
Hi,@Anon4343
If my answer is helpful to you, please mark it as the answer so that other users can refer to it. Thank you for your support and understanding.
We determined that if you disable the default Frontend receive connector for security reasons, you need to create a new receive connector for the server to use.