This problem is usually related to POP authentication procedure. When you attempt to send mail, the system requires that you authenticate to the server first. The way the server does this is that it first requires you to log into your pop account with the username and password you created when the pop account was set up through the mail manager. After you authenticate by logging in you have a period of 15 minutes to send mail. After this 15 minutes expires you will need to re-authenticate – if you don’t you get an error message.
This may sound more complicated than it actually is. For instance, when Outlook is opened it automatically presents you with a username and password box. After you type these in, Outlook does the rest. Usually, you can just send and receive mail, and Outlook will automatically resubmit your username and password combo. However, it does so only when you hit the send/receive button. If you only hit the send button your password is never resubmitted. Typically the password is only required when receiving (popping) mail. As you can see the process defaulted to by Outlook is backward with respect to our authentication procedures. Outlook first sends mail and then receives mail. This is where the failure comes in. On our system, you need to authenticate (receive) first and then send it.