If you have changed your email password, you will need to update that password for your Apple Mail to be able to download/send emails.
Also see: https://support.apple.com/en-gb/mail for more information.

iPhone/iPad
- Go to the Settings app
on your iPhone. - Scroll down and tap Apps
- Scroll down and then tap Mail.
- Tap Mail Accounts, then tap on your email account
- Click on Re-enter Password
- Type in your new password.
- If your email server support OAuth2 token-based authentication [Google, Yahoo, Outlook) it will open a web browser tab to complete your authentication.
- Enter your email address
- Enter your password or use a passkey if setup
- Check and accept access request options (may be multiple screens) to allow Apple Mail to access your email.
- Save the changes
- Close and reopen the Apple Mail app to force a refresh with the email server.
Reference: https://support.apple.com/en-my/guide/iphone/iph44d1ae58a/26/ios/26
macOS
Access your Internet Accounts by either
- Opening Mail
- Select Mail then Accounts
- Opening System Settings by clicking on the Apple icon in the top-left corner of your screen
- Select System Settings then Internet Accounts
Select your email Account
- Type in your new password.
- If your email server support OAuth2 token-based authentication [Google, Yahoo, Outlook) it will open a web browser tab to complete your authentication.
- Enter your email address
- Enter your password or use a passkey if setup
- Check and accept access request options (may be multiple screens) to allow Apple Mail to access your email.
- Save the changes
- Close and reopen the Apple Mail app to force a refresh with the email server.