Sometimes the emails you send via Kalix go to SPAM. We do everything we can to avoid this, like electronically signing the emails and having the opt-in system with an unsubscribe option. However, considering so much SPAM out there, it is difficult to avoid this happening altogether.
Whether or not an email is classified as SPAM really does depend on the email server the message is sent to. That is why Kalix has the opt-in system; this lets clients deal with any problems upfront. For example, they can find it in their spam and then mark it as 'not spam' so that your important messages like appointment reminders go through into their inbox as expected.
Steps clients can take to ensure your emails always arrive in their inbox.