Email providers try to protect you from the 293 billion spam emails sent on a daily basis (2019 figures). Most of these emails won't reach your email account at all, but if they do, they are put in your spam folder.
Sometimes email providers make mistakes and a legitimate email finds its way into your spam.
You can whitelist specific email addresses to stop their emails going into your spam box.
We have made a guide for each of the three most common email providers below. If your email provider isn't listed, have a look at the guides below to see if there is a similar method for your email provider.