Contracting out of the use of electronic signatures

If you want to make it absolutely clear that your company will only regard itself bound by a conventional notice, you must stipulate in your contract of employment that 'signed' refers to a hand-written signature

In this article on my website I mentioned that a person can resign by sms or email
Section 12 of the Electronic Communications and Transactions Act states the following:
A requirement in law that a document or information must be in writing is met if the document or Information is-
(a) in the form of a data message; and
(b) accessible in a manner usable for subsequent reference…
An SMS qualifies as a data message and so this SMS did satisfy the "in writing" requirement in the applicant's employment contract and his resignation by SMS was effective.
Emails, like SMS's, are data messages and it is certainly possible for an employee to resign by email provided the email satisfies the test of whether it evidences a clear and unequivocal intention to resign.  
If you want to make it absolutely clear that your company will only regard itself bound by a conventional notice, you must stipulate in your contract of employment that 'signed' refers to a hand-written signature, excluding any signature appended by 'electronic communication' as defined in the Electronic Communications and Transactions Act, no. 25 of 2002.
You may want to take a leaf from this disclaimer at he foot of an email I received from the Star Newspaper:
NOTICES:
1. This message and any attachments are confidential and intended solely for the addressee. If you have received this message in error, please notify the sender at the specific Independent Newspapers division, from which this message emanates, immediately. Any unauthorized use, alteration or dissemination is prohibited.
2. Independent Newspapers (Pty) Limited (Registration Number 1989/004672/07), including any one of its subsidiaries from which this message emanates, accepts no liability whatsoever for any loss whether it be direct, indirect or consequential, arising from information made available and actions resulting there from.
3. Please note that Independent Newspapers (Pty) Limited and all its subsidiaries only bind themselves by way of signed agreements. 'Signed' refers to a hand-written signature, excluding any signature appended by 'electronic communication' as defined in the Electronic Communications and Transactions Act, no. 25 of 2002.