No document is authentic unless signed by the author. This is the normal rule. Since "resignation" is concerned with the contract of employment between the employer and the employee, it is proper and not merely "safe" to have a signed "resignation letter", especially when there are times when employees have denied their own signatures and have alleged "duress" and "force" as the cause of resignation. It is advisable to insist upon a written and signed resignation.
Since it is a matter connected with the contract of employment, it is entirely possible, though not advisable, to make a stipulation in the contract of employment to the effect that the resignations received through email will be treated as authentically owned by the named sender. In such a case of prior awareness of the possibility of resignation forwarded through email being accepted, it is fine to receive/accept resignation through email.
To my mind, there is no case law on the exact point, but on the subject of resignations alleged to have been obtained under duress or force, there is case law. It is, however, extremely difficult to prove duress, force, or compulsion.
Regards,
Samvedan
December 13, 2005