Hi. I am using the free ddns service and also the dynu nameservers to point to my domain. I have a small mail server at home but all the emails I send go to spam. I am getting a perfect score on the mail testers as I have fulfilled all conditions. I have been trying to fix these for the last three days and the last few messages work with gmail but not with yahoo. In fact the latest ones do not even go to the yahoo junk folder as they used to but just vanish. I searched on several blocking lists as well, I cannot find my domain listed there. I have tried everything so please help. The only thing left I could think of is the fact that dynu nameservers might be caught in some list somewhere or they might have a filtering list themselves. Is this at all possible? I am a beginner so I really don't know what else to do. Thank you.

This issue is unlikely to be related to name servers. Email delivery depends on your MX records, SPF records, DKIM signature, sending IP reputation etc.

You seem to have set up MX records, SPF records, dmarc and DKIM successfully. You may confirm it by viewing the email that reached Gmail in its plain text format (Show original).

The rejection of Yahoo could be because your emails are sent from a dynamic IP address. You could try our SMTP outbound relay service at https://www.dynu.com/en-US/Email/Outbound-SMTP-Relay to see if it resolves your issue.

I thinking having a reverse DNS for the IP address the same as hostname of MX record is also helpful to avoid the email being detected as SPAM.

Thanx for the answers. My yahoo messages did arrive meanwhile. However they all ended up in the spam folder. I do have rdns set up properly. Also, my dns is not dynamic. I am getting 10/10 on mail tester. All seems perfectly set up. Still all mails are seen as spam by yahoo. Any ideas whom should I try to contact for this issue?

EDIT: Well, this is odd. I found the dynu reply/confirmation in the junk folder as well. The one containing the #ticket number. But not the other ones. What gives??

Email content may also cause it to be red flagged and treated as spam.

I know, this is why all my tests include no hyperlinks, weird/repeated characters, attachments - just to be on the safe side, for testing purposes. Also I copy/paste a lorem ipsum text (only), about a paragraph long. Other wellknown email domains accept my messages without troubles.