If you are receiving bounce back emails from Gmail, your IP address might be on the Gmail blacklist.
What are the reasons for the IP blacklist in Gmail?
There is no standard list of reasons from google that can block your IP Address. However, you can consider the below list, which can cause your IP block at google.
- Multiple Spam reports from Gmail users.
- High bounce rate.
- High outgoing email volume.
- Poor Sender Score.
- IP listings in public blacklists.
You can also check the public RBLs to verify if your IP Address for blacklist. Google may take signals from these public RBLs. How to check IP blacklist in public RBLs?
What are the precautionary steps you should take to avoid IP blacklist in Gmail?
You can take care of the below-mentioned precautionary steps to avoid IP blacklist in Gmail. It can also help you to prevent IP blacklist in RBLs as well.
- Ensure that email authentication records (SPF & DKIM) are correctly set for all the domains and are correct.
- Enable SMTP server logs on your server for port 25. How to check the SMTP log?
- Check email users' bulk forwarding to Gmail and stop unnecessary email forwarding.
- Verify your email list and remove the forged and duplicate entries. Also, don't rent any third-party email list.
- Ensure that all the email account on the server has strong passwords.
- Disable auto relay for SMTP on the server.
- If you are running an email marketing campaign, make sure you are using a double opt-in list. Please refer to what is the double opt-in list?
How to remove IP Address from Gmail blacklist?
If your email service IP address is blocked on Gmail, you will receive the bounce back email with SMTP error code 421 or 550.
Example of 421 bounce back
421 4.7.0 [173.xxx.xxx.xx] 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 https://support.google.com/mail/answer/188131 for more information. u22si16671234pfl.244 - gsmtp
Example of 550 bounce back
SMTP error from remote mail server after end of data: host gmail-smtp-in.l.google.com [192.xxx.xxx.xx]: 550-5.7.1 [193.XXX.XXX.125] 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 http://www.google.com/mail/help/bulk_mail.html to review 550 5.7.1 our Bulk Email Senders Guidelines. k8si8849879lbl.62
Once you receive the bounce email mentioned above, you should take the precautionary actions we have discussed earlier. After that, fill out the bulk sender form of Gmail. It will ask for the name, email address, and bounce back email header. You won't get any response from google after submitting the form, so don't need to worry. Google may take 13-15 days to unblock the IP Address.