Return address and mail-tester?

Question

Email

Hello colleagues.
After the online store moved to a new hosting, letters from the robot began to fall into spam on all popular mail services.
At first they tried to figure it out with the help of hosting technical support and the people who made the site for us, but they blame each other, and the problem remains in place.
When I realized that the issue was not being resolved, I registered a new user on the site, and indicated the address mail-tester.com by mail of this user.
Here are the test results
After reviewing them, I think that the problem is most likely in the return address, which for some reason is listed as [email protected]
Now I again wrote to the site developers, and they replied that there are no such settings in the UMI.CMS platform and write to the hosters. Hosters write that they hear about these settings for the first time, and they don’t know where it is prescribed ...
If there are knowledgeable people, tell me which way to dig?

Answer 1

Of course the problem is in the sender's address. If you owned the example.com domain, or at least it resolved on the same IP address as your site, then there would be no problems.
You might as well use [email protected] as the sender to make people feel flattered that Bill Gates himself wrote them the letter.
Definitely the problem is in those who created the site, when they send letters, they must indicate both the recipient's address and the return address of the sender. And they had to replace the default [email protected] with whatever was needed.
Show them the documentation
There is a line

//Указываем, от чьего имени придет письмо
 $mail->setFrom("[email protected]", "umisoft world wide empire");

Answer 2

The problem of many shared hosting. To avoid this kind of problems and have full control - you need a VPS.
https://habrahabr.ru/post/114852/