what is dead.letter ??

Hi all can you please help me what is dead.letter file ?
when it is created ? for the first time i have seen this file getting created in my current directory?

I am using SunOs.

Any IDEA ??

Some email user agents create this file as a temporary file when you draft an email, but do not send it yet. I know the 'pine' mailer does this. Are you using pine?

May be the pine was there but i found that you have some mail
then i type mail to see what it is ?
then what i did was mistakely i type r

some time later i found that DEAD

Any way thanks for clue could be because of that it did happen