Emails sent to spam folder

I use App Sheets to send automated emails. I send emails every weekday, and recipients can read them. However, on weekends (Saturday and Sunday), the emails I send end up in the spam folder. This happened on Saturday and Sunday, March 7th and 8th, and it’s happening again today, Saturday. Can anyone explain this to me?

Handling of spam is entirely controlled by your email provider. You’ll need to talk to them.