Email not arriving on your phone
If your email works on your computer but not your phone, the account is fine. The phone has lost its sign-in.
What's usually going on
This usually happens after a password change, a security prompt that was dismissed, or a software update that reset something. The account itself is almost never broken. One device has simply stopped being trusted.
Worth trying first
Check it's only the phone.
Open your email in a web browser on a computer. If it works there, the account is fine and the phone just needs to sign in again.
Look for a prompt.
Open the mail app, then your phone's Settings. A message asking you to re-enter your password, or one reading "Account Error", is the phone telling you exactly what it needs.
Restart the phone.
It's a cliché because it works. It forces the mail app to reconnect from scratch.
Remove the account and add it again.
Open Settings and search for "accounts". Remove the email account, then add it back. With Gmail, iCloud, Outlook, and Microsoft 365, your mail lives on the server, so nothing is lost. If your account is an older type called POP, stop and ask first.
When to hand it over
If the phone keeps rejecting a password you know is right, if security codes are going to a number you no longer have, or if it's a work account with rules you didn't set. That's a short job for us and a long afternoon for you.
Your own technologist, on call.
Tell us a little about your setup. We'll take it from there.