Welcome to Android Central! Which email provider? You may have to check the email account's server settings in the email app, and compare them with the correct settings from the provider. Open the Email app, tap Menu>Settings, select the email account, and look for the option to edit the server settings. Do a Google search for "[your email provider] IMAP/POP3 settings," and compare them with what you see in the email app. For outgoing email, the SMTP server settings are the important ones. Make sure your email password is entered for the SMTP server.