Registration validation emails rejected by Gmail

[cfish]

Up until recently, all emails sent by the forum were being received by all email services. Now, emails sent to users with Gmail accounts are being rejected. This seems to affect validation emails, password recovery emails etc. Anyone registering with a Gmail account is effectively locked out of the forum. I believe some security changes were made at Gmail on 30th May, the last successful registration via Gmail on my forum took place on 28th May, so I'm guessing this may be the cause. I'm using the PHP method to send emails, so I don't understand why emails that were previously getting through are now being rejected. Is anyone else seeing a larger than usual number of failed registrations?

[cfish]

I should probably add that this does not appear to be an IP blacklist issue, as I am able to send an email using the same outgoing mail server to Gmail addresses without problem. This issue seems only to affect emails from the forum.

[opentype]

What’s the exact error message?

Try sending a test mail from the ACP to https://www.mail-tester.com and check the results. 

[cfish]

Thanks @opentype, the results of that test = "Your email may never see the light of an inbox" 2.2/10

The problem flagged is that the mail server is not fully authenticated - looks like a problem with the MX record being used for PHP emails. If I use the same check from an address on the same domain via Outlook, I get 9/10 and no problems. I'm guessing that if I switch to SMTP mode, that should resolve the issue?

[opentype]

Yeah, that’s a terrible score. Switching to SMTP will probably fix it, but it also has disadvantages like slowing down replies. You can probably also get a perfect score with PHP Mails, but that will depend on your host, your DNS settings and so on. I won’t be able to tell you how to do it from a distance. 

[cfish]

That's a great help. Now that I know the root of the problem, I should be able to resolve it with my host. In the short term, I'll switch to SMTP and then work on improving the score for PHP mail. Thanks for your input, much appreciated.

[cfish]

2 hours ago, opentype said:

You can probably also get a perfect score with PHP Mails

@opentype It turns out that a perfect score is not possible with PHP. SpamAssassin automatically adds a value of -2.499 to any message sent via a PHP script, so even if everything else is perfect, the maximum score is 7.5. Simply changing my settings to SMTP increased the score from 2.2 to 8.9, and now Gmail is accepting emails sent from the forum.

[opentype]

30 minutes ago, cfish said:

@opentype It turns out that a perfect score is not possible with PHP. SpamAssassin automatically adds a value of -2.499 to any message sent via a PHP script …

That’s not true. Here is an example from one of my communities, tested again just a second ago. 

Achieved just using Invision Community with the PHP mail option. (But optimized with SPF, DKIM and DMARC records.)

Technically, there is no such thing as a “PHP mail” or an “SMTP mail”. Those are just different ways to initiate the email. But no option is intrinsically better or worse. 

But if you are fine with using SMTP, I guess we don’t need to debate these things. 

Edited June 12, 2022 by opentype

[hmikko]

From 7th of June Google blocks all emails which domain doesn’t have a correct SPF record. Received an email about that from my host. Maybe adding your host spf will help:

v=spf1 a mx include:spf.myukcloud.com ip4:5.134.11.72 ip4:5.134.14.73 ~all

Adding DKIM and DMARC will make it even better.