Send & Receive Issues

How to Fix Gmail Error 550.5.7.350 Rejections from Microsoft 365

Kushani Nimanthika Sep 29, 2026 869 views

Question details

Users need to resolve email delivery failures where Gmail rejects messages sent from a Microsoft 365 domain with error code 550.5.7.350.

How to Fix Gmail Error 550.5.7.350 Rejections from Microsoft 365

Product: Microsoft 365
Device & OS: not provided
Scenario: Sending outbound emails from a Microsoft 365 domain to Gmail accounts after a recent domain compromise or spam incident.
Observed behavior: Gmail rejects the incoming emails with error 550.5.7.350, indicating poor sender domain reputation. Correcting authentication alone does not immediately restore email delivery.

Before you start

Ensure you have Microsoft 365 Global Administrator privileges to review audit logs, secure user accounts, and update your domain's DNS records.

Solution 1Recommended

Secure Compromised Accounts and Review M365 Settings

Stop unauthorized email activity at the source by securing accounts, removing malicious forwarding rules, and reviewing outbound spam reports.

The most common cause of a damaged domain reputation is a compromised account sending spam. You must completely secure your environment before your reputation can begin to recover in Gmail.

Reset user passwords

Identify any compromised users in the Microsoft 365 Admin Center and immediately force a password reset and revoke all active sign-in sessions.

Remove unauthorized forwarding rules

Check the Exchange Admin Center for any suspicious inbox rules or connectors that might be silently forwarding or sending unauthorized emails.

Review outbound spam reports

Log into Microsoft Defender and navigate to the Outbound Spam report to identify which accounts have been triggering spam alerts and block them from sending further mail.

Secure Compromised Accounts and Review M365 Settings

Microsoft Support Limitations: Microsoft cannot directly contact Google to remove the block or change your domain reputation. You must fix the underlying issue and wait for Google's systems to re-evaluate your domain.

Solution 2

Verify and Align SPF, DKIM, and DMARC

Ensure your domain's email authentication meets Google's strict sender guidelines to establish trust and improve your domain reputation.

Solution 3

Monitor Domain Reputation with Google Postmaster Tools

Use Google's official tools to track your domain's reputation recovery and analyze spam rates.

Free Microsoft Office alternative

Enhance Your Productivity with WPS Office

While resolving domain reputation issues between Microsoft 365 and Gmail, consider switching to WPS Office. It provides a lightweight, free, and highly compatible suite for all your daily document, spreadsheet, and presentation needs.

1. Download the Installer: Visit the official WPS Office website and download the free installation package for your operating system.
2. Install WPS Office: Run the installer file and follow the quick on-screen instructions to set up the suite on your device.
3. Open and Edit Office Files: Launch WPS Office to easily open, edit, and save your existing Microsoft Office documents without format loss.

Completely free and lightweight alternative to Microsoft OfficeSeamless compatibility with Microsoft Word, Excel, and PowerPoint formatsAll-in-one workspace for documents, spreadsheets, and PDFsFamiliar user interface requiring zero learning curve

microsoft office alternative - wps office

Frequently Asked Questions

Can Microsoft support bypass or remove the Gmail 550.5.7.350 block?

No. The reputation block and the resulting 550.5.7.350 error are controlled entirely by Google's systems. Microsoft cannot directly remove the block or reset your domain's reputation in Gmail.

How long does it take for a domain's reputation to recover in Gmail?

Reputation recovery varies based on email volume and user behavior. Once you stop all spam activity, secure accounts, and correctly align SPF, DKIM, and DMARC, it typically takes several days to a few weeks of consistent, positive email sending to restore your reputation.

Is configuring SPF, DKIM, and DMARC enough to immediately fix the rejection?

No. While correct authentication (SPF, DKIM, DMARC) is mandatory according to Google's sender guidelines, it will not instantly reset a poor domain reputation caused by a recent spam incident. It is only the first step in the recovery process.

Are there any temporary workarounds while the domain reputation recovers?

As a temporary measure, the receiving organization or user can add your domain or email address to their safe senders allow-list, provided their organization's IT policies permit it. However, this must be done on the recipient's side.

Outlook & Email Problems