You have it the wrong way. Noone can make it so that gmail accepts their e-mail. It's the gmail's job after it receives the connection to process the SMTP commands and deliver the message to you.

I mean, assumming that the sender doesn't have broken SMTP client or doesn't follow standards.

It's gmail's user's problem if they don't accept mail or check their Junk folder or use an e-mail provider that they can't contact to solve issues on their side.

In the old days, if I didn't receive mail because my mail provider was rejecting it, it was me who had to talk to them. Free has a cost. And it's gmail users who should be paying it in their time and fruitless attempts at communicating with google. At least they'd realize what company they're enabling and how much it doesn't care about their e-mail.

We are a relatively small company and we operate our own mail server, mostly out of a shared belief in data privacy among myself and our staff. We self-host most of our tooling (mail, internal chat, Gitlab, CI/CD, and so on). It turns out this is all pretty simple given modern virtualization infrastructure and, in my estimation, has many upsides versus the alternatives.

That said, like the OP, despite having DKIM, SPF, proper DNS, and every other measure applied, it's conceivable that gmail might reject some emails from us. I don't have any memory of that actually happening, but I have heard stories like the OP's several times. It's a fairly common topic in conversation forums about self-hosting email servers. I don't expect the situation to change any time soon—I don't expect Google to change their ways and it would require significant pain for me to surrender to the gmail hegemony.

Gmail's spam filters always err on the false positive side. It's always been like that. Add the opaque nature of google operations, and you can't in good faith place the deliverability burden on third parties. It's like trying to hit bullseye in darts in pitch black darkness.

Best to assume gmail is flawed, which it is, as the parent poster did. At some point Google will realize the image problem and act.

Judging by what ends up in my gmail, very few people "can deliver to gmail" in any kind of reliable fashion. It depends entirely on how messed up the spam filtering is for individual accounts. The only reason I'm still on Gmail is that it's so entrenched in my life that tidying things up to move is a massive pain and will take a long time (and no, forwarding is not a reliable solution; my experience is that even forwarding from one gmail account to another will invariably cause some mail to go the spam folder of the account you forward from - yes there are options that are meant to prevent this; no they don't work reliably, and haven't in the years I've been using it, so it means one more place to check mail).

> A biz that can't deliver to gmail is a terrible smell though.

If anything, it means that teams are probably too independent and that there is no central approval process for things like sending emails.

For example, a lot of companies use products like Greenhouse. I am sure this will send email from your domain on your behalf. If you don't know what you have to talk to the DNS administrators to add a bunch of TXT records to enable that, you will just notice that some percentage of emails never get delivered (or if the product doesn't tell you that they're bouncing, you may never know. how could you?)

If you use something like Zendesk, you'll note how many people have been burned by this. By default, they end up using something like support.yourdomain.com because despite detailed instructions on how to set up the necessary DNS records to send email from youdomain.com, people still fail to do it right and then complain "nobody ever sees my support tickets".

My point is, email has been abused so heavily that it is somewhat difficult to set up a working system. That was my experience when I ran my own email server. Although I did OK with delivery, I also aggressively filtered messages and used greylisting. This broke a lot of broken email systems, whose administrators immediately blamed me. (I had a long back-and-forth with some company that wanted to hire me. Their email system was super broken. They blamed me and said that they weren't interested in a programmer that couldn't set up a mail server. LOL.)

In the past year or so, pulling non-spam out of my gmail spam folder has become routine. Previously it was very rare that legitimate mail ended up in my spam folder, including personal mail from my father from an email address he's been using for decades. A biz that call's gmail's problem gmail's problem is not a terrible smell.