oogle tried to deliver your message, but it was rejected by the server for the recipient domain [Moderator note: personal info removed].mail.protection.outlook.com [52.101.145.0].

Question

Message details

Subject:

Fwd: [Moderator note: personal info removed] INVOICES

Sender:

Recipient:

2 recipients

Date:

Feb 2, 2026, 4:21:49 PM

Message ID:

[Moderator note: personal info removed] 

Message Size:

160.62 KB

Attachments:

2

Direction:

Received

Status:

0/2 Delivered

Recipient details

Feb 2, 2026, 4:21:51 PM

2 seconds

Bounced

Feb 2, 2026, 4:21:49 PM

Received from an SMTP server with IP address: [Moderator note: personal info removed] (TLS enabled)

250 2.0.0 OK

Feb 2, 2026, 4:21:49 PM

Inserted into Gmail delivery pipeline

Feb 2, 2026, 4:21:50 PM

Dropped

Matched rules:

Routing: [Moderator note: personal info removed].outlook.com

Go to this setting

Feb 2, 2026, 4:21:50 PM

Received from an SMTP client with IP address:[Moderator note: personal info removed] (TLS enabled)

Feb 2, 2026, 4:21:50 PM

Bounced

Google tried to deliver your message, but it was rejected by the server for the recipient domain [Moderator note: personal info removed] .outlook.com [52.101.145.0].

 

The error that the other server returned was:

501 5.5.4 Invalid domain name [PN1PEPF000062BA.INDPRD01.PROD.OUTLOOK.COM 2026-02-02T10:51:52.332Z 08DE60A8F189E6CF]

Feb 2, 2026, 4:21:51 PM

Bounced

Google tried to deliver your message, but it was rejected by the server for the recipient domain [Moderator note: personal info removed].outlook.com [52.101.145.0].

 

The error that the other server returned was:

501 5.5.4 Invalid domain name [PN1PEPF000062BA.INDPRD01.PROD.OUTLOOK.COM 2026-02-02T10:51:52.332Z 08DE60A8F189E6CF]

Feb 2, 2026, 4:21:51 PM

2 seconds

Bounced

Answer 1

Hi @Satya Prakash Pandey

Thank you for posting your question in Microsoft Q&A. 

Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data. 

As your description, looks like your Gmail account is generating a delivery‑failure notice when you try to email a recipient whose domain is protected by Microsoft Outlook/Exchange Online. 

You could try to: 

Send the email again 

Make sure the recipient’s email address is typed correctly, with no typos or extra characters. 

Try composing a completely new email rather than forwarding or replying. 

Send it again using your regular email client or Gmail Web to avoid routing issues. 

Reach out to the recipient through another channel 

If the message continues to bounce, try contacting the recipient directly (in person, phone call, messaging app). 

Ask them to check whether: 

Their Microsoft 365 email service is experiencing issues.

Their mailbox is active and able to receive messages normally.

There are any restrictions, blocks, or filtering rules affecting incoming mail.

Please understand that our initial reply may not always immediately resolve the issue. However, with your help and more detailed information, we can work together to find a solution. 

---

Note: Please follow the steps in [our documentation] to enable e-mail notifications if you want to receive the related email notification for this thread. 

Answer 2

The error message you received indicates that the email sent to the recipient domain [Moderator note: personal info removed].outlook.com was rejected due to an invalid domain name. The specific error code 501 5.5.4 Invalid domain name suggests that the domain name provided in the email was not recognized or is incorrectly formatted.

Here are a few steps you can take to troubleshoot this issue:

1. Verify the Recipient's Email Address: Ensure that the email address you are trying to send to is correct and properly formatted.
2. Check Domain Configuration: If you have access to the domain settings, verify that the domain is correctly configured to receive emails and that there are no issues with its DNS records.
3. Contact the Recipient: If possible, reach out to the recipient through another means to confirm their email address and check if they are experiencing any issues with their email service.
4. Review Email Routing Rules: If you manage the sending domain, check the routing rules in your email system to ensure they are set up correctly for sending emails to the recipient's domain.

If the issue persists, you may want to consult your email administrator or the support team for further assistance.