Offline mode prevents you from getting new mail
Many mail applications offer an "offline" mode. This allows you to read and compose messages without connecting to the internet. For example, if you are using a dial-up connection, you could compose several messages and then connect to the internet only when you are ready to send them.
In mail clients that support multiple mailboxes, this also offers a way to disable a mailbox.
If you are unable to send or recieve mail, check to see if your mail client is in "offline" mode. This can happen if your computer was unable to establish a connection to your mail server for any reason. Some clients -- like Apple Mail -- are more likely to go into offline mode without warning than others.
You can enable or disable the ability to Access e-mail in offline mode in your e-mail program.
