Send & Receive Issues

How to Fix Gmail Error 550 5.7.350 for a Rejected Domain

Emma Brown Oct 8, 2026 868 views

Question details

Users are experiencing email delivery failures to Gmail and other major providers with Error 550 5.7.350 due to low sender reputation or suspected spam.

How to Fix Gmail Error 550 5.7.350 for a Rejected Domain

Product: Email Provider / Microsoft 365
Device & OS: not provided
Scenario: Sending outbound emails to Gmail, Yahoo, or AOL from a custom domain.
Observed behavior: Outbound messages are rejected with Error 550 5.7.350, even if a DMARC policy is already configured on the sending domain.

Before you start

Ensure you have administrative access to your domain's DNS settings and your email provider's admin center before making authentication changes.

Solution 1Recommended

Configure and Align SPF, DKIM, and DMARC Records

Proper email authentication is strictly required by Gmail and other major providers to prevent spam and verify your sender identity.

Merely having a DMARC record published is not enough to guarantee delivery. Your domain must also have valid SPF and DKIM records that strictly align with your sending domain to establish a positive sender reputation and bypass spam filters.

Verify SPF (Sender Policy Framework)

Log in to your DNS hosting provider's management console and ensure your SPF TXT record includes all authorized IP addresses and third-party senders, such as Microsoft 365.

Generate and Publish DKIM Keys

Access your email provider's admin panel (such as the Microsoft 365 Defender portal) to generate DomainKeys Identified Mail (DKIM) keys, then publish the provided CNAME records in your DNS settings.

Align Your DMARC Record

Review your DMARC record to ensure it aligns with both SPF and DKIM. Set your policy to monitor (p=none) initially, moving to enforcement (p=quarantine or p=reject) only after confirming legitimate emails are passing authentication.

Configure and Align SPF, DKIM, and DMARC Records

DNS Propagation Time: Keep in mind that any modifications made to your domain's DNS records can take up to 48 hours to fully propagate across global networks.

Solution 2

Monitor Domain Reputation and Follow Sender Guidelines

Consistently monitoring your domain's reputation helps identify and resolve spam-related blocking issues proactively.

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Frequently Asked Questions

Why am I getting Error 550 5.7.350 from Gmail?

This error occurs when Gmail rejects your email because your sending domain has a low reputation or is suspected of sending spam. It usually indicates missing, misconfigured, or misaligned SPF, DKIM, and DMARC authentication records.

Will adding a DMARC record automatically fix my email delivery?

No. While DMARC is strictly required by providers like Gmail and Yahoo, it relies entirely on SPF and DKIM. You must configure all three correctly, and they must align. Furthermore, if your domain already has a poor reputation, it may take time for delivery rates to improve.

How can I check if my SPF and DKIM are configured correctly?

You can use free online DNS lookup tools or email authentication validators like Google Postmaster Tools or MXToolbox to verify that your SPF and DKIM records are published, correctly formatted, and actively propagating.

What should I do if my Microsoft 365 emails are still blocked after updating DNS?

If you use Microsoft 365, review the Microsoft Defender outbound spam policies to ensure your account hasn't been compromised or restricted. Verify your DNS records through the Microsoft 365 admin center, and submit a request to Microsoft to unblock your tenant if necessary.

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