Email DNS Gmail e-mail delivery problem

Somehow mails can't be delivered to gmail. It is a huge problem. My users who register with gmail don't get activation mails or when someone gets a new pm, they don't get the e-mail reminding them this.

• I am using cloudflare for DNS.
• Zohomail for mail.
• Centminmod for the server.

Error:

Code:

<xxx@gmail.com>: host gmail-smtp-in.l.google.com[74.125.140.27] said:
550-5.7.1 This message does not have authentication information or fails to
pass 550-5.7.1 authentication checks. To best protect our users from spam,
the 550-5.7.1 message has been blocked. Please visit 550-5.7.1
https://support.google.com/mail/answer/81126#authentication for more 550
5.7.1 information. x2si10647871wmk.38 - gsmtp (in reply to end of DATA
command)
Reporting-MTA: dns; server.xxx.com
X-Postfix-Queue-ID: 5E83BB7AC1
X-Postfix-Sender: rfc822; info@xxx.com
Arrival-Date: Mon, 15 Apr 2019 14:35:21 +0000 (UTC)

Final-Recipient: rfc822; xxx@gmail.com
Action: failed
Status: 5.7.1
Remote-MTA: dns; gmail-smtp-in.l.google.com
Diagnostic-Code: smtp; 550-5.7.1 This message does not have authentication
information or fails to pass 550-5.7.1 authentication checks. To best
protect our users from spam, the 550-5.7.1 message has been blocked. Please
visit 550-5.7.1
https://support.google.com/mail/answer/81126#authentication for more 550
5.7.1 information. x2si10647871wmk.38 - gsmtp

What I have is DNS A, AAA, MX records and SPF, DKIM, DMARC





I didn't enable reverse DNS for the server (didn't know that I had to), I thought that might solve the problem, but did that today.





And this is the results from intodns.com

Spoiler

And then this is from mail-tester.com

Spoiler

Now you could say my SPF and DKIM are not configured. But:





I don't really know what else I can do. I tried everything and don't know what I am doing wrong here.

Would appreciate help.

 

Ah, now I understand the problem.

The whole time XenForo was sending the e-mails through Centmin Mod Postfix MTA, even though I haven't configured it.

I had to choose the SMTP option in XenForo settings in order to use zohomail. I thought choosing the default option in XF will do it just fine, but it didn't.

Now it seems okay, my mail goes through and lands in gmail. Also the mail-tester now gives me 9/10 points instead of 4. This was madness for me, such a simple thing... I am so stupid.

 

Is there a good reason also to set it up for the hostname now since I got it working for the domain?

Let me ask differently. What are the advantages of sending the mails though a 3rd party instead of Centmin mod?

Are there any advantages of setting BOTH ways to be able to send mails by configuring SPF/DKIM/DMARC for both?
Is one sufficient?