Mail from single-droplet getting unauthorized failures from reipient mail servers

I have a single droplet running my application, and hosting a postfix mail server for sending notifications, etc. However, mail is not working.

When I run a cmd-line test mail to a gmail account, I get a rejected response: “The IP you’re using to send mail is not authorized 550-5.7.1 to send email directly to our servers. Please use the SMTP relay at 550-5.7.1 your service provider instead.”

In terms of DNS record set-up: A records are fine for site and mail subdomain, as verified by MX record also verifies (now using main domain) I have three TXT records as follows: main site: v=spf1 -all mail._domainkey subdomain: “v=DKIM1;h=sha256;k=rsa;p=…” _dmarc subdomain: v=DMARC1;p=quarantine

The DKIM above matches my public/private setup, as per the DO “How To Install and Configure DKIM” tutorial.

I do receive email, I just cannot send any. Help appreciated! Fergus

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Bobby Iliev
Site Moderator
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October 6, 2021
Accepted Answer


It sounds like that your PTR record might be the problem

I could suggest following the steps from this answer here by @alexdo on how to setup a PTR record:

Once this is done, you might have to wait for the DNS cache to clear over the Globe, and then you could give it another try.

Let me know how it goes. Best, Bobby

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