Why I'm getting Spam emails?

Hi there, my forms are sending emails thought the Spam. Such as contact form as forgot password. I have read about the hosting provider but it's was working correctly before we worked to put it multiple languages. Can you please give an idea about what can cause this issue?. Haven't touch the email sending. It's untouched but suddenly it starts to send the emails thought the Spam or junk mail if is Microsoft account. I tested it also by downgrade my php and isn't working.

Spam filters work differently on different email providers. They can mark as spam if the FROM address doesn't use the same domain that the email was sent FROM, or if the proper SPF, and DKIM records aren't being created and set properly. Spam can also be triggered if your SMTP server's IP address has been added to an email black-list for sending SPAM, or because of the specific content of the email triggering a spam filter.

You can try using a service like: https://www.mail-tester.com/ to test your emails and they will tell you how likely a server would be to mark it as spam and why.