unable to send email to a Gmail address

[stefanwirtz]

Hi. This is the Mailer program at mail.123.com.

I'm afraid I wasn't able to deliver your message
"H2 Group Agent Request R7L Logistics LLC"
to the following addresses.

This is a permanent error; I've given up. Sorry it didn't work out.

Intended Recipients: 123@gmail.com
Failure Reason: Error: 550 5.7.25 [2604:a00:11:4573:216:3eff:fe2f:5a3d] The IP address sending this 5.7.25 message does not have a PTR record setup, or the corresponding 5.7.25 forward DNS entry does not match the sending IP. As a policy, Gmail 5.7.25 does not accept messages from IPs with missing PTR records. For more 5.7.25 information, go to 5.7.25 https://support.google.com/a?p=sender-guidelines-ip 5.7.25 To learn more about Gmail requirements for bulk senders, visit 5.7.25 https://support.google.com/a?p=sender-guidelines. af79cd13be357-7e8542c26b9si182336285a.597 - gsmtp

[stefanwirtz]

The reverse DNS address at my VPS provider is correctly showing mail.123.com and all Cloudron email settings show green checkmarks.

In an effort to troubleshoot, I tried setting up a free external SMTP Server on one of my domains through mailersend.net and after sending an email, I did not get any error message, but the email also did not reach its intended recipient.

[stefanwirtz]

I hope there is an easy & not too technical solution to this issue... if it gets too technical & complicated I will have to resort to hosting my email elsewhere

[robi]

Gmail is sensitive to SPAM and does many checks on the connecting mail server.

As the message says there is a problem with your PTR from their perspective.

Make sure to check IPv4 and IPv6 PTR as they check both.

[murgero]

If you just setup the domain, server, and cloudron please note DNS and PTR can take up to 48 hours to take full effect.

[stefanwirtz]

thank you for your input, I am double checking IPV4&6 with my VPS provider right now

[stefanwirtz]

My VPS provider indicated the IPV6 address is missing on Cloudflare. I have now added the AAAA record at both root and mail level and am now giving it some time to propagate before trying to send the email to gmail again. Further I am deleting the temporary smtp server Mailersend. Hopefully this solves the problem and will inform you later how it went. Thank you

[stefanwirtz]

Update: I am now able to send emails WITHOUT receiving an immediate error message, however, the email is not arriving in the recipient's email inbox or spam..any ideas?

[stefanwirtz]

Ah, I just realized that on Cloudron, for the domain in question, I had to switch from external smtp back to built-in smtp...let's see if this does the trick...can you tell I am a non-techie??

[stefanwirtz]

...and BINGO, I can now send email to Gmail...message was received in the INBOX. We can now close this ticket. Thank you for your help and I am so glad I can keep email hosted on Cloudron.