What do you mean by "the info file'? When you write "it won't work on my iMac", do you mean in the Mail application? If so, open Mail's preferences, select the "Accounts" panel, then look for the password for the "incoming mail server". There should also be a password for the "outgoing mail server". To see that, pull down the list named that way at the bottom of the window, select "Edit SMTP Server List", select your SMTP server, then select the "Advanced" tab. If there's a password there, then change it also.