You can use the likes of https://www.mailgenius.com/ https://www.mailgenius.com/ to test an email and it'll let you know why it's hitting the spam. It can be a

You can use the likes of https://www.mailgenius.com/ https://www.mailgenius.com/ to test an email and it'll let you know why it's hitting the spam. It can be anything from trigger words in the subject/content to the email being image heavy etc. Usually checking the headers of the email when it's been sent to spam can identify why.