How to solve the problem of emails getting into SPAM?

Question

Google

Dear colleagues.
Once again, I ran into the problem of getting emails into SPAM.
This time I couldn't solve it. I wonder how you deal with this and how you remove your projects from SPAM lists and how do they get there?
Initial data
1. Mail servers from which messages are sent are not in SPAM lists.
2. The IP address from which emails are sent matches the MX-record of the mail server domain.
3. The outgoing address matches the mail server address.
4. The mail with which the letter comes also exists.
5. The domain was registered new and did not get into SPAM lists and other black lists.
6. No more than 10 letters were sent from this domain, and all of them had different content.
7. Emails immediately end up in SPAM from Google and Hotmail.
8. I registered the project on Google, installed all the necessary codes.
Emails still end up in SPAM. Alas, because of this, the whole project is to hell, since the whole point is that people generate personal calendars and send them to friends.
I would be grateful for any information and help.
Thanks in advance.
Edgar.

Answer 1

Start by cleaning up the DNS:
1.
$ host 109.95.208.165
165.208.95.109.in-addr.arpa domain name pointer www.colocat.ru
$ host www.colocat.ru
www.colocat.ru has address 109.95.208.164
2.
$ host 94.228.168.67
67.168.228.94.in-addr.arpa domain name pointer mail.colocat.ru.
$ host mail.colocat.ru
mail.colocat.ru has address 109.95.208.165

Answer 2

you can also add a TXT record v=spf1 +a +mx -all

Answer 3

I think we should look at bondbig's question about PTR
The first thing to know The main points when setting up corporate mail

Answer 4

Do your mailers have a PTR record? Must exist, if possible, match MX.

Answer 5

Good question. I'll find out and write back.

Answer 6

Yes, it exists and matches.

Answer 7

Well, take a look at the headers of a spam message, some mailers write in them why it got into spam.
Well, in general, use an external, but reliable smtpshnik and do not beat your brains.