What messages are you talking about? Emails? What email client and OS are you using? Please give us some more specific information and we help you more.
Yes please provide more specifics. <b>IF</b> this is Outlook and you are set up with POP3 accounts with your ISP then you need to make sure you have selected to “leave a copy of messages on the server” in your account profile. Otherwise you are downloading the emails to one or the other machine that you are using at the time and therefore the other machine will not get that same message.