Sometimes can receive email sometimes cannot from the same sender

It sounds like you are experiencing intermittent email delivery issues with your corporate email account. Here are a few potential reasons for this situation:

1. Temporary Delivery Issues: The message you received from Gmail indicates that there was a temporary problem delivering your message. This could be due to various factors, including network issues or server problems on the recipient's side.
2. Email Filtering: Sometimes, emails can be filtered out by spam filters or other security measures. Since you mentioned that you checked your spam folder, it may be worth checking if any filtering rules are set up in your corporate email account that might be affecting delivery.
3. Domain Configuration: If the domain is new or recently added to Microsoft 365, it may take time for the domain to replicate across all servers, which could affect email delivery. This process can take up to an hour for the domain and up to 72 hours for DNS records to propagate fully.
4. Message Trace: You can use the message trace tool in Microsoft 365 to see if there are any records of the emails sent from your Gmail account. This can help identify if the emails were received and processed by the server.
5. Throttling Issues: If there is suspicious activity detected from the sending IP address, Microsoft may temporarily restrict mail from that source, which could lead to delivery failures.

If the issue persists, consider reaching out to your IT support team for further investigation, as they may have access to more detailed logs and tools to diagnose the problem.

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Hi @Cincia Tan 

Thank you for reaching out to Microsoft Learn Q&A!  

Based on the domain you provided, I used a public DNS checker to review your configuration. The result shows that your domain does not have an MX record, which is essential for sending and receiving emails. 

Please double-check your DNS settings and ensure that the required records are added as recommended in this article: Add DNS records to connect your domain - Microsoft 365 admin | Microsoft Learn 

As suggested in the Q&A, you can investigate the mail route to your organization by signing in to the Exchange Admin Center and navigating to Mail flow > Message trace. 

After you have verified your DNS configuration and if you require specialized support from the Microsoft Support Team urgently, you can reach out to them using one of the following methods: 

Option 1: Contact via Phone  

You may need to reach out via the customer service phone number: Customer service phone numbers - Microsoft Support.    

Important Note: You may first interact with an AI assistant before being connected to a human agent. Please answer the questions carefully to ensure you're routed correctly. Having your information ready will help speed up the process.  

Please be aware that this team is often handling a high volume of cases. It may take 3–10 business days for them to get back to you.   

Option 2: Create a ticket via another tenant  

If you have access to another Microsoft 365 tenant, you can submit a support ticket through the Microsoft 365 Admin Center.     

I sincerely hope this information helps clarify your situation and supports you in planning your solution. Please don’t hesitate to reply if you have any updates.  

Thank you for your understanding.  

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