How to Remove Your IP Address from Gmail’s Blacklist

How to Remove Your IP Address from Gmail's Blacklist

One of the common reasons the emails do not reach the target Gmail recipients is the blocking of the email sender by Google. If you are not able to deliver emails to your Gmail subscribers, then this article will surely help you.

Why Google Can Block You

Though Gmail does not disclose their email filtering rules, below are some common reasons why Gmail may reject email coming from your server.

If you are doing any of the below things, then you appear to be sending spam. As a result, Gmail may block your server’s IP address.

The most common reasons are:
  • Large volumes of emails sent from a new IP address.
  • Sudden changes in email volume.
  • High bounce rate.
  • Spam reports from Gmail users.
  • Incorrect DNS Settings.
  • Low Sender Score.
  • IP listings in public blacklists.

Google may use signals from these public blacklists, so you can start by checking if your IP is on any of them: – includes dynamic and non mail server IP ranges. – includes emails that Spamhaus has identified as spam. – includes bots and exploit agents. – includes emails sent to spam traps or reported by their users as spam.

You can use the GlockApps IP Blacklist Checker to run your IPs against these and other blacklists.

IP reputation monitor checks all major blacklists in the industry and alarms if the IP gets blacklisted.

Read more: Email Marketer’s Guide: What You Need to Know about Gmail

Your Gmail Blacklist Investigation Process

To identify whether or not your inability to deliver emails to your Gmail users is related to blocking issues, follow the steps below:

  • Check your SMTP server logs for 500 errors.
  • Check logs for blocks to other ESPs and public blacklists.
  • Run an IP blacklist check.
  • Use an email spam checker to see your server’s sending reputation.
  • Check for user’s bulk forwarding email to and related domains.
  • Check for any newsletters or newsgroups that originate from the server.
  • Identify any bulk marketing campaigns that may be on the server.
  • Verify that authentication records (PTR, DKIM, SPF) are correct.
  • Find out if the email volume to Gmail has increased.

If you are blocked by Gmail, your email will be rejected with a 421 or 550 SMTP error.

421 errors indicate temporary blocks and mail servers attempt to resend the emails. If you correct the issue, then these blocks can be resolved automatically. On the other hand, if the issue is left unaddressed, Google may decide to block your email entirely.

Example of a 421 error:

421 4.7.0 [ 15] Our system has detected that this message is suspicious
due to the nature of the content and/or the links within. To best protect our users from spam,
the message has been blocked. Please visit
for more information. u22si16671234pfl.244 - gsmtp

550 errors are permanent failures. You will have to take some action before Gmail removes your server IP address from their blacklist.

Example of a 550 error:

SMTP error from remote mail server after end of data:
host []:
550-5.7.1 [194.XXX.XXX.181] Our system has detected an unusual rate of
550-5.7.1 unsolicited mail originating from your IP address. To protect our
550-5.7.1 users from spam, mail sent from your IP address has been blocked.
550-5.7.1 Please visit to review
550 5.7.1 our Bulk Email Senders Guidelines. k8si8849879lbl.62

Here’s the full list of Gmail error codes:

421, “4.4.5”, Server busy, try again later.
421, “4.7.0”, IP not in whitelist for RCPT domain, closing connection.
421, “4.7.0”, Our system has detected an unusual rate of unsolicited mail originating from your IP address.
421, “4.7.0”, Temporary System Problem. Try again later.
421, “4.7.0”, TLS required for RCPT domain, closing connection.
421, “4.7.0”, Try again later, closing connection.
450, “4.2.1” The user you are trying to contact is receiving mail too quickly.
450, “4.2.1”, The user you are trying to contact is receiving mail at a rate that prevents additional messages from being delivered. Please resend your message at a later time. If the user is able to receive mail at that time, your message will be delivered.
451, “4.3.0”, Mail server temporarily rejected message.
451, “4.3.0”, Multiple destination domains per transaction is unsupported. Please try again.
451, “4.4.2”, Timeout – closing connection.
451, “4.5.0”, SMTP protocol violation, see RFC 2821.
452, “4.2.2”, The email account that you tried to reach is over quota.452, “4.5.3”, Domain policy size per transaction exceeded, please try this recipient in a separate transaction.
452, “4.5.3”, Your message has too many recipients.
454, “4.5.0”, SMTP protocol violation, no commands allowed to pipeline after STARTTLS, see RFC 3207.
454, “4.7.0”, Cannot authenticate due to temporary system problem.
454, “5.5.1”, STARTTLS may not be repeated.
501, “5.5.2”, Cannot Decode response.
502, “5.5.1”, Too many unrecognized commands, goodbye.
502, “5.5.1”, Unimplemented command.
502, “5.5.1”, Unrecognized command.
503, “5.5.1”, “EHLO/HELO first.
503, “5.5.1”, MAIL first.
503, “5.5.1”, RCPT first.
503, “5.7.0”, No identity changes permitted.
504, “5.7.4”, Unrecognized Authentication Type.
530, “5.5.1”, Authentication Required.
530, “5.7.0”, Must issue a STARTTLS command first.
535, “5.5.4”, Optional Argument not permitted for that AUTH mode.
535, “5.7.1”, Application-specific password required.
535, “5.7.1”, Please log in with your web browser and then try again.
535, “5.7.1”, Username and Password not accepted.
550, “5.1.1”, The email account that you tried to reach does not exist. Please try double-checking the recipient’s email address for typos or unnecessary spaces.
550, “5.2.1”, The email account that you tried to reach is disabled.
550, “5.2.1”, The user you are trying to contact is receiving mail at a rate that prevents additional messages from being delivered.
550, “5.4.5”, Daily sending quota exceeded.
550, “5.7.0”, Mail relay denied.
550, “5.7.0”, Mail Sending denied.
550, “5.7.1”, Email quota exceeded.
550, “5.7.1”, Invalid credentials for relay.
550, “5.7.1”, Our system has detected an unusual rate of unsolicited mail originating from your IP address.
550, “5.7.1”, Our system has detected that this message is likely unsolicited mail. To reduce the amount of spam sent to Gmail, this message has been blocked.
550, “5.7.1”, The IP you’re using to send mail is not authorized to send email directly to our servers. Please use the SMTP relay at your service provider instead.
550, “5.7.1”, The user or domain that you are sending to (or from) has a policy that prohibited the mail that you sent. Please contact your domain administrator for further details.
550, “5.7.1”, Unauthenticated email is not accepted from this domain.
552, “5.2.2”, The email account that you tried to reach is over quota.
552, “5.2.3”, Your message exceeded Google’s message size limits.
553, “5.1.2”, We weren’t able to find the recipient domain. Please check for any spelling errors, and make sure you didn’t enter any spaces, periods, or other punctuation after the recipient’s email address.
554, “5.6.0”, Mail message is malformed. Not accepted.
554, “5.6.0”, Message exceeded 50 hops, this may indicate a mail loop.
554, “5.7.0”, Too Many Unauthenticated commands.
555, “5.5.2”, Syntax error.

See the full list of the Gmail’s SMTP error codes here

How to Request Removal from Gmail’s Blacklist

If you send legitimate bulk emails and get bounces with the 400 error code, you need to go through Google’s Bulk Sender Guidelines and then complete the Bulk Sender Contact Form

Going through Bulk Sender Guidelines pay attention to these sections:

  • Authentication;
  • Subscription and unsubscribing;
  • Proper email formatting;
  • Third-party senders and affiliate marketing programs.

After you made sure you are following all the best practices, you can proceed to fill out a Bulk Sender Contact Form.

In a Bulk Sender Contact Form, you will have to follow these steps:

  1. Fill out your name, email address, and the reason: message incorrectly classified as spam, SMTP temp-fails or rejects, or other (there is a field to specify what exactly).
  2. Press ‘Next’ to see the second screen. Here you will have to write two versions of your problem – a short one and a detailed one.
  3. It is also required to add headers from messages you sent to a Gmail or Google app user and that was marked as spam/phishing. The fresher the message the better, but it can’t be older than 12 days. Now you can submit your form.

Note, that usually Gmail does not reply to the submission so don’t worry, they process the submitted form, although it may take up to 15 days.

Also, it is recommended that you sign up for a Google postmaster account and check your sending domain reputation with Google. You will get access to several dashboards: Spam Rate Dashboard, Domain and IP Reputation Dashboard, Feedback Loop Dashboard (only for senders who implemented the Gmail Spam Feedback Loop), Authentication Dashboard, Delivery Errors Dashboard.

Want to know about a blacklisting problem the moment it occurs? I recommend using the IP Reputation Monitoring at GlockApps. This way you’ll receive instant notifications when an issue appears and start delisting before it turns into a serious problem.

With GlockApps Uptime Monitor free trial, you get:

  • 15 Monitors;
  • 1-minute monitoring intervals;
  • HTTP/TCP/TLS Monitors;
  • SPF/DKIM/DMARC Monitors;
  • IP Reputation Monitor;
  • Instant notifications.

Start Free Trial

Read also: How to Remove Your IP Address from the Hotmail/Outlook’s Blacklist How to Remove Your IP Address from the Yahoo!’s Blacklist



Julia Gulevich is an email marketing expert and customer support professional at GlockSoft LLC with more than 15 years of experience. Author of numerous blog posts, publications, and articles about email marketing and deliverability.