It's a good idea to check your spam folders on a regular basis so you don't miss important emails. Email Service Providers (like Google, Yahoo, AOL, etc.) are getting increasingly aggressive in blocking spam, which results in a greater percentage of legitimate email getting blocked.
The steps below differ by email provider. Click or tap on the name of your email provider below for more detailed instructions. If your provider isn't listed, try to google it using a search term such as "how to add email to contact list xyz.com" or "how to add email to my safe list".