Gmail "550-5.7.28 ... unusual rate of unsolicited mail from your IP address": how to fix it

What it means

Gmail has seen a lot of unwanted email coming from your IP address in a short time, and it now refuses mail from that IP. The bounce usually looks like this:

550-5.7.28 [203.0.113.10] Our system has detected an unusual rate of
550-5.7.28 unsolicited mail originating from your IP address. To protect our
550-5.7.28 users from spam, mail sent from your IP address has been blocked.
550-5.7.28 Please visit https://support.google.com/mail/?p=UnsolicitedIPError
550 5.7.28 to review our Bulk Email Senders Guidelines.

You may first see a temporary version with code 421-4.7.28, which means Gmail is limiting your IP. The 550 version is a refusal: Gmail will not retry. This block is about the IP address, so every email from that server is affected, not just one campaign.

Why it happens

• A compromised account. A stolen mailbox password lets spammers send through your server. This is the most common cause on small servers.
• A hacked website or form. A contact form, plugin or script is abused to send thousands of emails.
• A big campaign to a poor list. Bought, rented or very old lists generate complaints and bounces quickly.
• Shared IP. Another customer of your hosting or email provider is sending spam from the same IP.
• Open relay. A misconfigured server accepts and forwards mail for anyone.

How to check

• Send a test email: on the Delivmail home page (/), copy your unique test address and send it a normal email from the same server, tool or mailbox that bounced. Open the report when it is ready.
• Check the blacklist section. An IP that Gmail blocks for volume is often also listed on public blacklists. You can also check it directly on /blacklists.
• Look at your mail queue and logs. Thousands of queued messages, unknown recipients or a single account sending far more than usual are clear signs of abuse.
• Use Google Postmaster Tools (postmaster.google.com) to see your spam rate and reputation, if you send enough to Gmail.

How to fix it

1. Stop the spam at its source. Find the account, form or script responsible. Change the password, enable two-factor authentication, disable or fix the form (add a captcha and rate limits) and update the website software.
2. Empty the queue of spam messages so they are not retried.
3. Check your server is not an open relay. Only authenticated users and your own applications should be allowed to send.
4. Request removal from public blacklists once the spam has stopped, following each list's process.
5. Make sure authentication is complete. SPF, DKIM and DMARC should all pass for your domain.
6. Fix your sending practices. Send only to people who opted in, remove bounced and unengaged addresses, add a clear unsubscribe link, and spread large sends over time.
7. If the IP is shared, contact your provider with the bounce message. They need to find the abusive customer or move you to a clean IP.

There is no Gmail form to remove this block. It lifts on its own once Gmail sees that the unwanted traffic has stopped.

Check that it is fixed

Send a new Delivmail test and confirm the IP is no longer on blacklists and that authentication passes. After a few days of clean sending, send a normal email to the Gmail address that bounced. If it still fails, keep volume low and check again later: recovery can take days to weeks. Never switch IPs just to escape the block.