Using techmology to ask for forgiveness

An old friend asked a similar question back in the late 90s, when e-mail was not yet ubiquitous. Now that e-mail is just one of many techmological methods to communicate, I'd like to revisit it.

The basic idea is, "how legitimate is asking forgiveness of your friends before Yom Kippur via e-mail, IM, text message?" Is there a hierarchy of acceptability? E-mail without a reply yes, text message with a reply yes, but IM without a reply no? How do you do it?