There are many reasons why an email may end up in the spam folder when sent from either your website or Webmail. The title and/or content of the email, attachments, links and the reputation of the sending domain can have an impact on whether an email goes into the spam folder.
Different email clients such as Gmail and Outlook have their own rules around emails and spam as do websites hosted on different servers with different firewalls. We suggest you make sure that any emails you send do not contain any titles, wording, links or attachments that email clients could consider spam.
Marking any emails that arrive in the spam folder in error not as spam is also a good way to help make sure the emails arrive in your inbox.