[kureikain]

It does but only for IPv4. If you have those:

- reverse ip. origin ip -> dns -> resolve to ip

- SPF

- DKIM

- DMARC

- Make sure ip are not on DNSBL

- Message ID

- Try to connect to gmail mx server using TLS

Then you have very low chance to get in spam unless you are sending spam and get blacklist. Time to time an gmail mx server will reject you, rate limiting, just try again with another and you will be ok.

Source: I run https://hanami.run and have to deal with this a lot due to nature of an email forwarding service that people usually use as one-off email ([e-mail] for their one-off service) so it attract a lot of spam which I have to filter and make sure it won't go to gmail/microsft

I would say gmail is the best among big provide: Microsoft/Apple(iclouds) are garbage mail server where they just blindly trust DNSBL and block you no matter what. Gmail was way better.

However, if you use IPv6, it's a bit harder to avoid being flag as spam. It's really random and I don't know why yet and I contacted them and now "Waiting for 2 weeks to get a response"

[alex_studer]

Out of curiosity, where do you send the emails from? (Are the IP addresses from AWS/some other large provider? Or something else?) I've heard that the IP address block has something to do with getting marked as spam.

I've checked everything on that list and it's all good, and I'm sending from IPv4. The really frustrating thing is that Google's own Postmaster Tools [0] doesn't want to tell me anything without "a sizable daily volume of email traffic (up to the order of hundreds)".

If it doesn't have to do with the origin IP's neighborhood, my only other guess is that I don't have enough email volume, which seems like a catch-22...

[0] https://gmail.com/postmaster/

[kureikain]

I used Hetzner.

At the time I allocate an IP address, it's was listed on DNSBL. I tried like 30times to get a good IP and gave up. I instead just allocate a new IP, wait a week. Started to send email to myself every 15minutes to a gmail address. Anytime it isn't showed up in Important, I go in to move it to important. If it showed up as spam, I marked it as not spam.

After 2-3 weeks doing that, The IP is no longer listed on any blacklist and I started to roll them out.

Don't worry too much about IP blacklist. They aren't super important to gmail. If an IP stopped sending spam, they will be removed from IP blacklist eventually. Give it a week.

> "a sizable daily volume of email traffic (up to the order of hundreds)".

I send about 8,000 emails per day and somehow that Postmaster Tools not reports anything at all. I would say

If you send me an email [e-mail] I can tell you what you can do to avoid being flagged at spam. Happy to jump in a 1-1 chat https://calendly.com/vinh-hanami/15min to help you on that.

[jacquesm]

Even replying to gmail messages or forwarding an older address to gmail will randomly fail. I've had some pretty important messages (for instance: invoices) randomly blackholed while all other mail arrived fine. It is super frustrating to answer someone's request for an invoice and to see that invoice then disappear without any notice that it was spam trapped.

[kureikain]

Yes, I heard you.

To gmail point of view, they don't care about forwarding or replying to an email someone send you at all. All they care seems is about the message follow standard best practice(SPF/DKIM/DMARC/PTR) and send from a good IP. Sometime your IP can be flagged as spam wrongly on DNSBL. But it's very easy to get remove from DNSBL. Just submit a removal request, explain your situation and it's usually remove within a few days.

Also, the reason while your important emails are marked as spam is depended on gmail mx server you connected to. I don't know the detail but I have seen gmail mx server rejected/spammed my email, but on subsequent try if I connect to different one(by resolving other MX record), the email went through just fine.

If you send me an email [e-mail] I can try to spot if anything may randomly flagged your email.

Also, did you have multiple SMTP servers?