ISP domain

[Raymond Orchison]

Hi,   I am in urgent need of some help. I have qmail installed on RedHat 6.0. I have an isdn line conected to my isp. The isdn line will come up every half hour or so.   My isp hosts my domain, all mail for my domain is stored with the isp until the isdn line comes up, the linux box will then issue the ETRN command to download all mail for my domain locally using fetchmail.   The question I have is how do I store all outgoing mail and then send it when the isdn line goes up?   Thank you   Raymond