[ic] How to send reminder email??

[interchange-users@interchange.redhat.com (Alma Nuker)]

Hi guys;

I am trying to work out how to send an reminder email?? For example
I want to send reminder email for maintenence 20 days before it is due
as well as 5 days before maintenenace is due.

Could you please point me in right directions?? I was looking on your
mailing list, but I was unable to find anything on this topic.

Any help would be welcome.

Thanks

Alma