i hope i have this problem, but email? seems impersonal and unprofessional. i would be offended if a firm notified me of a ding by email. calling, too, would be awkward.
shucks, i'm so fortunate to be so low class that i took the only offers i got so i was saved from this awkward situation.
why not send an email that personally describes reasons followed by a formal letter to confirm?
congrats on the multiple offers.
I received dings by e-mail, and even one ding by phone (!). Not a ding after callbacks, but a "we're not calling you back" after OCI, came by phone. And I also got callbacks via REGULAR mail. Weird.
In either the ding or callback/offer case though, I liked receiving the e-mail (vs. regular mail) because it helped me plan.
So when I decline offers, I think I will send e-mails (for speed) but follow up with a regular mail letter (to show sincerity).