mail scheduler

Dear all, sometimes I would like to send an E-Mail not immediately but at a later time. This can be scheduled with an "at" process from command line. But it would be more comfortable to compose the message with mutt and let mutt forward it to the at daemon. The principle seems to be easy. But I have absolutely no idea how to do it. Does anybody know if this can be done with a mutt macro? Or is there any other option? Best regards Joseph