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Email Drone: Gmail email deliverability issue

Our system has detected that this message is 550-5.7.1 likely suspicious due to the very low reputation of the sending IP 550-5.7.1 address. To best protect our users from spam, the message has been 550-5.7.1 blocked. Please visit 550 5.7.1 for more information. a126si2231200qke.133 - gsmtp (in reply to end of DATA command))

My mail server always get the above error message, and it lasts for more than one month, no matter I STOP postfix and let it has time to recovery.

Any suggestions? Thanks in advance.


Try adding your IP address to the whitelist. is the most well-known public whitelist. You can go to the self service page and register an account on the website, then add your mail server information. If you are lucky, your mail server’s IP address might be added to the whitelist.

After creating an account at DNSWL, you should click the DNSWL IDS tab to create an ID. Enter your domain name and verify the domain ownership. Then add your mail server IP address to your DNSWL ID.

Your IP address will not be added immediately to your DNSWL ID. Your change requests must be approved by DNSWL admins. Once approved, your IP address will appear in your DNSWL ID, which means your mail server IP address is added to the whitelist.

Thank you so much and I will try it as soon as possible. And also I will update it with you later. Thanks again.

Thanks a lot for your help on my Gmail deliverability issue. It looks the email can reach the Gmail Inbox from my email server which has the issue before. :+1:

Hi LinuxBabe,

Updating for the gmail deliverability issue.

I have add 2 DNSWL IDs, one group can reach the gmail immediately, but another one is still cannot reach the gmail inbox/spam. If you have time could you help to check this ip: And if there is any other works I need to do to make the ip forwards email locates into gmail’s. Thank you so much.



Just checked my email servers’ blacklist by MXTOOLSBOX, I am on the UCEPROTECTL3.

That’s incredible, all my servers on Digital Ocean ISP are on UCEPROTECTL3…, looks like I can do nothing for that.

Big well-known hosting providers like DigitalOcean or Vultr are abused by spammers.

I run my mail server on ScalaHosting. As you can see from the screenshot below, my mail server’s IP address ( isn’t on any blacklist.

And Gmail thinks my IP reputation is high.

You can follow the tutorial below to properly create a VPS server on ScalaHosting.
How to Create a Linux VPS Server on ScalaHosting