That requirement can be satisfied by a message from that person’s computer which includes a scan of their signature or simply adding a typed name, provided it is intended by the person to serve as a signature and acceptance of the content of the message. A contract signed in this way, again subject to specific exceptions, will be valid and enforceable.
There is a distinction between an electronic signature and an advanced electronic signature which is only available through an accredited agency and includes a secure process with specific software to secure the message.