I can’t send or receive emails from any of my accounts

Did you try all the things in your referring article? --> If you can't receive email on your iPhone, iPad, or iPod touch - Apple Support

Are you using iCloud mail, or are you using a third party mail service? If using iCloud mail, can you see your mail by logging into iCloud.com? Use iCloud Mail on iCloud.com - Apple Support

If using a third party service, can you see your mail using whatever method they may provide for online viewing?