Whenever service of notice is required by Sections 1400, 1508, and 1509, such notice may be given and be complete by depositing the same with the United States Mail, addressed to the employer at his last known address. If represented by counsel in the proceedings before the Director, then service of notice may be made upon such employer by mailing same to such counsel. If agreed to by the person or entity entitled to notice, notice may be given and completed electronically, in the manner prescribed by rule, by posting the notice on a secure web site accessible to the person or entity and sending notice of the posting to the last known e-mail address of the person or entity.